Make LANGUAGE switchable in runtime (#653)

squashed into a single commit because doing it in steps that all
compiled involved a lot of boilerplate that is pointless to commit to
the repository. GH still has the PR for reference.

g_lang, MAX_MESSAGES_ON_MAP_BOTTOM, and GetLanguagePrefix() were
compile-time constants selected by the ENGLISH/GERMAN/... build
define. They're now runtime, defaulting to the same per-exe value the
define used to pick, and overridable at startup from [Ja2 Settings]
LANGUAGE in Ja2.ini.

-

XMLTacticalMessages is filled at runtime from NewTacticalMessages.xml,
never from compiled-in per-language data: all 8 per-language definitions
were the identical all-zero { L"" }. Delete them and define one shared
buffer in Utils/XML_Language.cpp (the loader) instead of pointer-rebinding
it like the static tables — this drops 9 dead 800KB zero-buffers (8
namespaced copies in LanguageStrings.cpp plus the standalone one) and
leaves no bind-ordering hazard for the XML load path.

-

ExportStrings.cpp privately recompiled one language's full text table
by #including the raw _<LANG>Text.cpp inside namespace Loc, keyed off
the exe-level ENGLISH/GERMAN/... compile macro (whichever the build
happened to select). That's redundant with the pointer globals every
other subsystem already uses (Text.h / LanguageStrings.cpp).

Drop the private copy; the unqualified table names in Loc::ExportStrings
now resolve to the global pointer externs, which BindLanguageStrings has
already rebound to the runtime g_lang by the time this runs (EXPORT_STRINGS
ini flag, checked after GetRuntimeSettings in sgp.cpp). gs_Lang (used only
by Loc::Translate for the Polish/Russian byte remap on raw .edt exports) is
now derived from g_lang via ToLocLanguage, so the export always matches
whatever language is actually active instead of a compile-time pick.

-

Editor/popupmenu.cpp and Strategic/Scheduling.cpp kept their own
call-site extern of gszScheduleActions as CHAR16[NUM_SCHEDULE_ACTIONS][20]
after the real definition changed into a rebindable pointer
(CHAR16 (*)[20], LanguageStrings.cpp). MSVC decays the outer array
dimension when mangling globals, so both declarations produce the same
symbol (?gszScheduleActions@@3PAY0BE@_WA) and the mismatch linked
silently -- but the array-typed TUs then indexed the 4-byte pointer
slot itself as string data, so the editor schedule popup and the map
schedule message text read garbage.

-

add text.def to be single-source of truth on symbol names and use it
 .much simpler, less error prone if adding more strings

-

add pseudo interface for language state. MAX_SAGES_ON_BOTTOM must always
 change in lockstep with g_lang. this isn't foolproof but better

---------

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Editor/Cursor Modes.h

@@ -29,7 +29,7 @@ void IncreaseSelectionDensity();
 void DecreaseSelectionDensity();
 void RemoveCursors();
 
-extern STR16 wszSelType[6];
+extern STR16 *wszSelType;
 
 extern BOOLEAN gfCurrentSelectionWithRightButton;
 
@@ -40,4 +40,4 @@ extern BOOLEAN gfCurrentSelectionWithRightButton;
 
 #endif
 
-#endif
+#endif

Editor/EditorMercs.h

@@ -325,7 +325,7 @@ extern UINT8 gubCurrMercMode, gubPrevMercMode;
 
 #define NUM_DIFF_LVLS						5
 
-extern STR16 zDiffNames[NUM_DIFF_LVLS];
+extern STR16 *zDiffNames;
 extern INT16 sCurBaseDiff;
 extern INT16 gsSelectedMercID;
 extern INT32 gsSelectedMercGridNo;

Editor/popupmenu.cpp

@@ -40,7 +40,7 @@ MOUSE_REGION popupRegion;
 UINT16 gusEntryHeight;
 BOOLEAN fWaitingForLButtonRelease = FALSE;
 
-extern CHAR16 gszScheduleActions[ NUM_SCHEDULE_ACTIONS ][20];
+extern CHAR16 (*gszScheduleActions)[20];	// NUM_SCHEDULE_ACTIONS entries
 
 //Finds the string for any popup menu in JA2 -- the strings are stored
 //in different ways in each instance.