check for missing statfs() prototype (happens at least under AIX 4)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@35288 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/unix/utilsunx.cpp

@@ -80,6 +80,11 @@
     #endif // __BSD__/!__BSD__
 
     #define wxStatfs statfs
+
+    #ifndef HAVE_STATFS_DECL
+        // some systems lack statfs() prototype in the system headers (AIX 4)
+        extern "C" int statfs(const char *path, struct statfs *buf);
+    #endif
 #endif // HAVE_STATFS
 
 #ifdef HAVE_STATVFS