Fix crash when using wxThreadSpecificInfo from global object ctor.

When not using compiler TLS support (which is the default now), TLS variable
itself needs to be initialized and user-defined code in the global objects
ctor could be called before this happened, resulting in using uninitialized
CRITICAL_SECTION under Windows and a crash.

Fix this by wrapping global wxThreadSpecificInfo itself in an accessor
function ensuring that it is always initialized before use.

Notice that this required adding wxTLS_TYPE_REF() as wxTLS_TYPE() itself can't
be used for the function return value (__thread or similar can only be used on
the variables).

Closes #16009.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_3_0_BRANCH@75948 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/tls.h

@@ -44,6 +44,7 @@
 
 #ifdef wxHAS_COMPILER_TLS
     #define wxTLS_TYPE(T) wxTHREAD_SPECIFIC_DECL T
+    #define wxTLS_TYPE_REF(T) T&
     #define wxTLS_PTR(var) (&(var))
     #define wxTLS_VALUE(var) (var)
 #else // !wxHAS_COMPILER_TLS
@@ -135,6 +136,7 @@
     };
 
     #define wxTLS_TYPE(T) wxTlsValue<T>
+    #define wxTLS_TYPE_REF(T) wxTLS_TYPE(T)&
     #define wxTLS_PTR(var) ((var).Get())
     #define wxTLS_VALUE(var) (*(var))
 #endif // wxHAS_COMPILER_TLS/!wxHAS_COMPILER_TLS