crt: Provide __p__wpgmptr() function for VC20+ CRT import libraries

Function __p__wpgmptr() returns pointer to global variable _wpgmptr and is
available since VC20, it is available also in UCRT, and also in x86 version
of OS system version msvcrt.dll.

crtdll.dll and msvcrt10.dll do not provide global variable _wpgmptr and
neither __p__wpgmptr() function.

For remaining CRT import libraries (x64/arm32/arm64 msvcrt.dll) provide
mingw-w64 version of __p__wpgmptr() function defined via global variable
_wpgmptr.

Global variable _wpgmptr is available in all CRT libraries except UCRT.

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

mingw-w64-crt/Makefile.am

diff --git a/mingw-w64-crt/Makefile.am b/mingw-w64-crt/Makefile.am
index 1b2d993..2d1ccb7 100644
--- a/mingw-w64-crt/Makefile.am
+++ b/mingw-w64-crt/Makefile.am
@@ -468,6 +468,7 @@
   misc/__p__pgmptr.c \
   misc/__p__wcmdln.c \
   misc/__p__wenviron.c \
+  misc/__p__wpgmptr.c \
   misc/_create_locale.c \
   misc/_free_locale.c \
   misc/_get_current_locale.c \
@@ -486,6 +487,7 @@
   misc/__p__mbctype.c \
   misc/__p__pgmptr.c \
   misc/__p__wcmdln.c \
+  misc/__p__wpgmptr.c \
   misc/_getpid.c \
   misc/initenv.c \
   stdio/_fstat64i32.c \
@@ -589,6 +591,7 @@
   misc/__p__mbctype.c \
   misc/__p__pgmptr.c \
   misc/__p__wcmdln.c \
+  misc/__p__wpgmptr.c \
   misc/_getpid.c \
   misc/initenv.c \
   stdio/_setmaxstdio.c \

mingw-w64-crt/misc/__p__wpgmptr.c

diff --git a/mingw-w64-crt/misc/__p__wpgmptr.c b/mingw-w64-crt/misc/__p__wpgmptr.c
new file mode 100644
index 0000000..5742236
--- /dev/null
+++ b/mingw-w64-crt/misc/__p__wpgmptr.c
@@ -0,0 +1,17 @@
+/**
+ * This file has no copyright assigned and is placed in the Public Domain.
+ * This file is part of the mingw-w64 runtime package.
+ * No warranty is given; refer to the file DISCLAIMER.PD within this package.
+ */
+
+#include <_mingw.h>
+#include <stddef.h>
+
+extern wchar_t** __MINGW_IMP_SYMBOL(_wpgmptr);
+
+wchar_t** __cdecl __p__wpgmptr(void);
+wchar_t** __cdecl __p__wpgmptr(void)
+{
+    return __MINGW_IMP_SYMBOL(_wpgmptr);
+}
+wchar_t** (__cdecl *__MINGW_IMP_SYMBOL(__p__wpgmptr))(void) = __p__wpgmptr;