Rename 'Standard Gaming Platform' to 'sgp' (#246)

* rename 'Standard Gaming Platform' to 'sgp'

* Adapt CMakeLists.txt files to renamed SGP directory

* Lowercase it

sgp/stringicmp.cpp

@@ -0,0 +1,26 @@
+//
+// Snap: Implementation of case-insensitive string comparison classes
+//
+#include "stringicmp.h"
+#include <ctype.h>
+
+
+
+bool TStringiLess::operator() (std::string const& s1, std::string const& s2) const
+{
+	// An MSVC compliance issue...
+	//using std::toupper;
+
+	const char *p1 = s1.c_str();
+	const char *p2 = s2.c_str();
+
+	while (*p1 && *p2 && toupper(*p1) == toupper(*p2)) {
+		++p1;
+		++p2;
+	}
+
+	if (!*p1) return *p2 != 0;
+	if (!*p2) return false;
+
+	return toupper(*p1) < toupper(*p2);
+}