build Lua from vendored source instead of the prebuilt lua51.lib

The tree carried two prebuilt Lua static libraries and a copy of the Lua
public headers. lua51.lib is 5.1.2 and matched the headers; lua51.vc9.lib
is 5.1.4 and was dead weight — it came second in Ja2_Libraries, so the
linker resolved every Lua symbol out of lua51.lib and never pulled an
object from it. Just as well, since it asks for /DEFAULTLIB:MSVCRT while
we build /MT.

ext/lua-5.1.5 is the upstream tarball unmodified, built as lua51 the way
the other vendored libraries are, and its src directory replaces lua/ as
the home of lua.h, luaconf.h, lauxlib.h and lualib.h. Those four headers
were stock 5.1.2 retabbed, so 5.1.5 is bugfix-only against what the game
compiled against; the bytecode format is unchanged across 5.1.x and every
script under gamedir is plain source anyway. lua/lua.hpp had no includers
and returns to etc/ where upstream keeps it.

/SAFESEH:NO goes with it. Its two stated reasons were lua51.lib and the
smackw32 import library, and both are now gone: every remaining prebuilt
static library is SAFESEH-clean (libexpatMT.lib 5 of 5 members with
@feat.00 = 0x1, RakNetLibStatic.lib 79 of 79), and lld-link emits a
3155-entry SEHandlerTable without it.

The /MT comment blamed the wrong library. lua51.lib carried no linker
directives at all; RakNetLibStatic.lib is what pins us to the static
runtime, with /DEFAULTLIB:LIBCMT and /DEFAULTLIB:libcpmt.

Verified by building all four applications in Debug and Release, and by
linking the tarball's own lua.c against our lua51.lib with the build's
clang-cl flags and running it under Wine: 5.1 stdlib, GC, coroutines and
the x86 __asm fld/fistp lua_number2int fast path all behave. The game
itself could not be launched here — this checkout's gamedir has loose
Data directories but no SLF archives, so VFS aborts on Data\Ambient.slf
long before any script runs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ext/lua-5.1.5/Makefile

@@ -0,0 +1,128 @@
+# makefile for installing Lua
+# see INSTALL for installation instructions
+# see src/Makefile and src/luaconf.h for further customization
+
+# == CHANGE THE SETTINGS BELOW TO SUIT YOUR ENVIRONMENT =======================
+
+# Your platform. See PLATS for possible values.
+PLAT= none
+
+# Where to install. The installation starts in the src and doc directories,
+# so take care if INSTALL_TOP is not an absolute path.
+INSTALL_TOP= /usr/local
+INSTALL_BIN= $(INSTALL_TOP)/bin
+INSTALL_INC= $(INSTALL_TOP)/include
+INSTALL_LIB= $(INSTALL_TOP)/lib
+INSTALL_MAN= $(INSTALL_TOP)/man/man1
+#
+# You probably want to make INSTALL_LMOD and INSTALL_CMOD consistent with
+# LUA_ROOT, LUA_LDIR, and LUA_CDIR in luaconf.h (and also with etc/lua.pc).
+INSTALL_LMOD= $(INSTALL_TOP)/share/lua/$V
+INSTALL_CMOD= $(INSTALL_TOP)/lib/lua/$V
+
+# How to install. If your install program does not support "-p", then you
+# may have to run ranlib on the installed liblua.a (do "make ranlib").
+INSTALL= install -p
+INSTALL_EXEC= $(INSTALL) -m 0755
+INSTALL_DATA= $(INSTALL) -m 0644
+#
+# If you don't have install you can use cp instead.
+# INSTALL= cp -p
+# INSTALL_EXEC= $(INSTALL)
+# INSTALL_DATA= $(INSTALL)
+
+# Utilities.
+MKDIR= mkdir -p
+RANLIB= ranlib
+
+# == END OF USER SETTINGS. NO NEED TO CHANGE ANYTHING BELOW THIS LINE =========
+
+# Convenience platforms targets.
+PLATS= aix ansi bsd freebsd generic linux macosx mingw posix solaris
+
+# What to install.
+TO_BIN= lua luac
+TO_INC= lua.h luaconf.h lualib.h lauxlib.h ../etc/lua.hpp
+TO_LIB= liblua.a
+TO_MAN= lua.1 luac.1
+
+# Lua version and release.
+V= 5.1
+R= 5.1.5
+
+all:	$(PLAT)
+
+$(PLATS) clean:
+	cd src && $(MAKE) $@
+
+test:	dummy
+	src/lua test/hello.lua
+
+install: dummy
+	cd src && $(MKDIR) $(INSTALL_BIN) $(INSTALL_INC) $(INSTALL_LIB) $(INSTALL_MAN) $(INSTALL_LMOD) $(INSTALL_CMOD)
+	cd src && $(INSTALL_EXEC) $(TO_BIN) $(INSTALL_BIN)
+	cd src && $(INSTALL_DATA) $(TO_INC) $(INSTALL_INC)
+	cd src && $(INSTALL_DATA) $(TO_LIB) $(INSTALL_LIB)
+	cd doc && $(INSTALL_DATA) $(TO_MAN) $(INSTALL_MAN)
+
+ranlib:
+	cd src && cd $(INSTALL_LIB) && $(RANLIB) $(TO_LIB)
+
+local:
+	$(MAKE) install INSTALL_TOP=..
+
+none:
+	@echo "Please do"
+	@echo "   make PLATFORM"
+	@echo "where PLATFORM is one of these:"
+	@echo "   $(PLATS)"
+	@echo "See INSTALL for complete instructions."
+
+# make may get confused with test/ and INSTALL in a case-insensitive OS
+dummy:
+
+# echo config parameters
+echo:
+	@echo ""
+	@echo "These are the parameters currently set in src/Makefile to build Lua $R:"
+	@echo ""
+	@cd src && $(MAKE) -s echo
+	@echo ""
+	@echo "These are the parameters currently set in Makefile to install Lua $R:"
+	@echo ""
+	@echo "PLAT = $(PLAT)"
+	@echo "INSTALL_TOP = $(INSTALL_TOP)"
+	@echo "INSTALL_BIN = $(INSTALL_BIN)"
+	@echo "INSTALL_INC = $(INSTALL_INC)"
+	@echo "INSTALL_LIB = $(INSTALL_LIB)"
+	@echo "INSTALL_MAN = $(INSTALL_MAN)"
+	@echo "INSTALL_LMOD = $(INSTALL_LMOD)"
+	@echo "INSTALL_CMOD = $(INSTALL_CMOD)"
+	@echo "INSTALL_EXEC = $(INSTALL_EXEC)"
+	@echo "INSTALL_DATA = $(INSTALL_DATA)"
+	@echo ""
+	@echo "See also src/luaconf.h ."
+	@echo ""
+
+# echo private config parameters
+pecho:
+	@echo "V = $(V)"
+	@echo "R = $(R)"
+	@echo "TO_BIN = $(TO_BIN)"
+	@echo "TO_INC = $(TO_INC)"
+	@echo "TO_LIB = $(TO_LIB)"
+	@echo "TO_MAN = $(TO_MAN)"
+
+# echo config parameters as Lua code
+# uncomment the last sed expression if you want nil instead of empty strings
+lecho:
+	@echo "-- installation parameters for Lua $R"
+	@echo "VERSION = '$V'"
+	@echo "RELEASE = '$R'"
+	@$(MAKE) echo | grep = | sed -e 's/= /= "/' -e 's/$$/"/' #-e 's/""/nil/'
+	@echo "-- EOF"
+
+# list targets that do not create files (but not all makes understand .PHONY)
+.PHONY: all $(PLATS) clean test install local none dummy echo pecho lecho
+
+# (end of Makefile)