Auto merge of #3319 - uniboi:main, r=JohnTitor

Add `_msize` for Windows targets

Creates a binding for `_msize` for windows targets

Author: bors

libc-test/semver/windows.txt

@@ -247,6 +247,7 @@ localtime_s
 lseek
 lseek64
 malloc
+_msize
 memchr
 memcmp
 memcpy

src/windows/mod.rs

@@ -345,6 +345,7 @@ extern "C" {
     pub fn strtoull(s: *const c_char, endp: *mut *mut c_char, base: c_int) -> c_ulonglong;
     pub fn calloc(nobj: size_t, size: size_t) -> *mut c_void;
     pub fn malloc(size: size_t) -> *mut c_void;
+    pub fn _msize(p: *mut c_void) -> size_t;
     pub fn realloc(p: *mut c_void, size: size_t) -> *mut c_void;
     pub fn free(p: *mut c_void);
     pub fn abort() -> !;