[Core] Ensure inline toupper/tolower (#1805)

Some standard lib headers (e.g. stdlib.h) end up setting __NO_CTYPE.
When ctype.h is processed with this flag different code is compiled,
amongst others making toupper/tolower and some isxxx() not inline
but calling extern functions (which is slower). Because of include
guards to ensure the inlining, ctype.h must be the first header file
included for a module.

Source/core/Portability.h

@@ -396,6 +396,8 @@ struct SEMAPHORE_BASIC_INFORMATION {
 #endif
 
 #ifdef __LINUX__
+#include <ctype.h> // must be first for inline ::tolower() etc.
+
 #include <cstddef>
 #include <cstdint>
 #include <cstdio>