define NAME_MAX for Windows

Summary:
If we have `PATH_MAX` we can probably have `NAME_MAX` as well.

It should be exact equivalent of `NAME_MAX` on Windows:
https://docs.microsoft.com/en-us/cpp/c-runtime-library/path-field-limits?view=msvc-160

Reviewed By: Orvid

Differential Revision: D26784071

fbshipit-source-id: 1e28d5de4358efded182db85f0382939c96a4dce

folly/portability/Stdlib.h

@@ -35,6 +35,7 @@ extern "C" {
 // code that needs them.
 #define PATH_MAX _MAX_PATH
 #define MAXPATHLEN _MAX_PATH
+#define NAME_MAX _MAX_FNAME
 
 char* mktemp(char* tn);
 char* mkdtemp(char* tn);