cairo-missing: Fix and cleanup ssize_t type definition

The definition of ssize_t is needed in cairo-missing.h and can be
dropped from files which include it.

perf/cairo-analyse-trace.c

@@ -55,8 +55,6 @@
 #ifdef _MSC_VER
 #include "dirent-win32.h"
 
-typedef SSIZE_T ssize_t;
-
 static char *
 basename_no_ext (char *path)
 {

perf/cairo-perf-report.c

@@ -44,12 +44,6 @@
 #include <libgen.h>
 #endif
 
-/* 'ssize_t' does not exist in the C standard on win32.
- * We use 'ptrdiff_t', which is nearly equivalent. */
-#ifdef _MSC_VER
-typedef ptrdiff_t ssize_t;
-#endif
-
 #ifdef _MSC_VER
 static long long
 strtoll (const char  *nptr,

perf/cairo-perf-trace.c

@@ -56,8 +56,6 @@
 #ifdef _MSC_VER
 #include "dirent-win32.h"
 
-typedef SSIZE_T ssize_t;
-
 static char *
 basename_no_ext (char *path)
 {

util/cairo-missing/cairo-missing.h

@@ -35,6 +35,14 @@
 
 #include <stdio.h>
 #include <string.h>
+#include <sys/types.h>
+
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+typedef SSIZE_T ssize_t;
+#endif
 
 #ifndef HAVE_GETLINE
 cairo_private ssize_t