headers: Add support for -D_TIME_BITS=64

Currently all 32-bit non-UCRT builds are forced to use time_t type as
32-bit and also all time_t functions in 32-bit form.

With this change, any msvcrt.dll based 32-bit application can use 64-bit
time_t functions by defining -D_TIME_BITS=64 flag during compilation.

Flag -D_TIME_BITS=64 is recognized also by GNU C library header files for
the same purpose.

When both _USE_32BIT_TIME_T and _TIME_BITS are defined by application then
_USE_32BIT_TIME_T override effect of _TIME_BITS.

Signed-off-by: Martin Storsjö <martin@martin.st>

mingw-w64-headers/crt/_mingw.h.in

diff --git a/mingw-w64-headers/crt/_mingw.h.in b/mingw-w64-headers/crt/_mingw.h.in
index a5399e0..c113c29 100644
--- a/mingw-w64-headers/crt/_mingw.h.in
+++ b/mingw-w64-headers/crt/_mingw.h.in
@@ -390,7 +390,7 @@
 
 #ifndef __WIDL__
 
-#if defined (_WIN32) && !defined (_WIN64) && !defined (__MINGW_USE_VC2005_COMPAT) && !defined (_UCRT)
+#if defined (_WIN32) && !defined (_WIN64) && !defined (__MINGW_USE_VC2005_COMPAT) && !defined (_UCRT) && !(defined (_TIME_BITS) && _TIME_BITS == 64)
 #ifndef _USE_32BIT_TIME_T
 #define _USE_32BIT_TIME_T
 #endif