[Mingw-w64-public] [PATCH] headers: undef register in case projects define it.

[Jeremy D. <jer...@us...>]

For example, doxygen defines `register` to shut up an error due to it being
deprecated/removed in ISO C++ 17, but that causes issues with this
construct, which is an extension and still supported.

Fixes: f0044963d7ba ("headers: Use register variable for NtCurrentTeb implementation on aarch64.")
---
Is this OK, or does it need any other preprocessor checks before using
push_macro/pop_macro?  I grepped for other usages and it seems like this
is how it's done...

 mingw-w64-headers/include/winnt.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mingw-w64-headers/include/winnt.h b/mingw-w64-headers/include/winnt.h
index b6d1f58ed..e6fdfac51 100644
--- a/mingw-w64-headers/include/winnt.h
+++ b/mingw-w64-headers/include/winnt.h
@@ -10211,7 +10211,10 @@ typedef DWORD (WINAPI *PRTL_RUN_ONCE_INIT_FN)(PRTL_RUN_ONCE, PVOID, PVOID *);
     PVOID GetFiberData(VOID);

 #if defined (__aarch64__) || defined(__arm64ec__)
+#pragma push_macro ("register")
+#undef register
     register struct _TEB *__mingw_current_teb __asm__("x18");
+#pragma pop_macro ("register")
     FORCEINLINE struct _TEB *NtCurrentTeb(VOID)
     {
         return __mingw_current_teb;
-- 
2.47.1.windows.1