MSVC: Add support for building with NO_MMAP

When the NO_MMAP build variable is set, the msvc linker complains:

    error LNK2001: unresolved external symbol _getpagesize

The msvc libraries do not define the getpagesize() function,
so we move the mingw_getpagesize() implementation from the
conditionally built win32mmap.c file to mingw.c.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

compat/mingw.c

@@ -1000,6 +1000,18 @@ repeat:
 	return -1;
 }
 
+/*
+ * Note that this doesn't return the actual pagesize, but
+ * the allocation granularity. If future Windows specific git code
+ * needs the real getpagesize function, we need to find another solution.
+ */
+int mingw_getpagesize(void)
+{
+	SYSTEM_INFO si;
+	GetSystemInfo(&si);
+	return si.dwAllocationGranularity;
+}
+
 struct passwd *getpwuid(int uid)
 {
 	static char user_name[100];

compat/mingw.h

@@ -166,7 +166,7 @@ int mingw_connect(int sockfd, struct sockaddr *sa, size_t sz);
 int mingw_rename(const char*, const char*);
 #define rename mingw_rename
 
-#ifdef USE_WIN32_MMAP
+#if defined(USE_WIN32_MMAP) || defined(_MSC_VER)
 int mingw_getpagesize(void);
 #define getpagesize mingw_getpagesize
 #endif

compat/win32mmap.c

@@ -1,17 +1,5 @@
 #include "../git-compat-util.h"
 
-/*
- * Note that this doesn't return the actual pagesize, but
- * the allocation granularity. If future Windows specific git code
- * needs the real getpagesize function, we need to find another solution.
- */
-int mingw_getpagesize(void)
-{
-	SYSTEM_INFO si;
-	GetSystemInfo(&si);
-	return si.dwAllocationGranularity;
-}
-
 void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
 {
 	HANDLE hmap;