Merge branch 'ss/msvc' into maint

Build updates for MSVC.

* ss/msvc:
  MSVC: use shipped headers instead of fallback definitions
  MSVC: vsnprintf in Visual Studio 2015 doesn't need SNPRINTF_SIZE_CORR any more

compat/mingw.h

@@ -406,7 +406,7 @@ static inline void convert_slashes(char *path)
 int mingw_offset_1st_component(const char *path);
 #define offset_1st_component mingw_offset_1st_component
 #define PATH_SEP ';'
-#ifndef __MINGW64_VERSION_MAJOR
+#if !defined(__MINGW64_VERSION_MAJOR) && (!defined(_MSC_VER) || _MSC_VER < 1800)
 #define PRIuMAX "I64u"
 #define PRId64 "I64d"
 #else

compat/snprintf.c

@@ -9,7 +9,7 @@
  * always have room for a trailing NUL byte.
  */
 #ifndef SNPRINTF_SIZE_CORR
-#if defined(WIN32) && (!defined(__GNUC__) || __GNUC__ < 4)
+#if defined(WIN32) && (!defined(__GNUC__) || __GNUC__ < 4) && (!defined(_MSC_VER) || _MSC_VER < 1900)
 #define SNPRINTF_SIZE_CORR 1
 #else
 #define SNPRINTF_SIZE_CORR 0

compat/vcbuild/include/unistd.h

@@ -45,11 +45,15 @@ typedef unsigned long long uintmax_t;
 
 typedef int64_t off64_t;
 
+#if !defined(_MSC_VER) || _MSC_VER < 1600
 #define INTMAX_MIN  _I64_MIN
 #define INTMAX_MAX  _I64_MAX
 #define UINTMAX_MAX _UI64_MAX
 
 #define UINT32_MAX 0xffffffff  /* 4294967295U */
+#else
+#include <stdint.h>
+#endif
 
 #define STDIN_FILENO  0
 #define STDOUT_FILENO 1