Revert "crt: Move stdio/[v]snprintf.c to libmsvcr*.a from libmingwex.a"

This reverts commit ae95d7ca7320f6a6dd27cf1633188103af71c372.

That commit mentioned splitting the aliases to separate object files as
an alternative solution. In b46a25b433f5adf23418994df484b2e6b3f9e566,
this was done, so the __ms_[v]snprintf functions can be moved back to
libmingwex as they themselves are harmless there.

This avoids needing to build a separate copy of [v]snprintf.o for each
of the msvcr* libraries.

This should fix cases when linking some object files built against
headers in msvcrt mode against ucrt. This isn't a supported configuration,
one can't in general link object files built for one crt mode against
another crt. However, if the only mismatch is use of __ms_[v]snprintf,
linking that against ucrt should be mostly harmless.
diff --git a/mingw-w64-crt/Makefile.am b/mingw-w64-crt/Makefile.am
index 20e65cf..a9dfd2e 100644
--- a/mingw-w64-crt/Makefile.am
+++ b/mingw-w64-crt/Makefile.am
@@ -169,9 +169,7 @@
   misc/uchar_mbrtoc32.c \
   misc/wcrtomb.c \
   stdio/acrt_iob_func.c \
-  stdio/snprintf.c \
   stdio/snprintf_alias.c \
-  stdio/vsnprintf.c \
   stdio/vsnprintf_alias.c \
   math/frexp.c
 
@@ -468,9 +466,9 @@
   stdio/mingw_snprintfw.c  stdio/mingw_sprintf.c     stdio/mingw_sprintfw.c   stdio/mingw_sscanf.c      stdio/mingw_swscanf.c   \
   stdio/mingw_vfprintf.c   stdio/mingw_vfprintfw.c   stdio/mingw_vfscanf.c    stdio/mingw_vprintf.c     stdio/mingw_vprintfw.c  \
   stdio/mingw_vsnprintf.c  stdio/mingw_vsnprintfw.c  stdio/mingw_vsprintf.c   stdio/mingw_vsprintfw.c   stdio/mingw_wscanf.c    \
-  stdio/mingw_wvfscanf.c   stdio/snwprintf.c        stdio/strtof.c            stdio/truncate.c        \
+  stdio/mingw_wvfscanf.c   stdio/snprintf.c          stdio/snwprintf.c        stdio/strtof.c            stdio/truncate.c        \
   stdio/ulltoa.c           stdio/ulltow.c            stdio/vasprintf.c        stdio/vfscanf.c           stdio/vfwscanf.c        \
-  stdio/vscanf.c           stdio/vsnwprintf.c        stdio/vsscanf.c         \
+  stdio/vscanf.c           stdio/vsnprintf.c         stdio/vsnwprintf.c        stdio/vsscanf.c         \
   stdio/vswscanf.c         stdio/vwscanf.c           stdio/wtoll.c            stdio/mingw_asprintf.c    stdio/mingw_vasprintf.c
 
 # these go into both 32 and 64 bit x86 versions: