Fixed build error with some Mingw configuration related to socklen_t

git-svn-id: https://svn.pjsip.org/repos/pjproject/trunk@2160 74dad513-b988-da41-8d7b-12977e46ad98
diff --git a/pjlib/include/pj/compat/os_auto.h.in b/pjlib/include/pj/compat/os_auto.h.in
index 6ce05d4..c963179 100644
--- a/pjlib/include/pj/compat/os_auto.h.in
+++ b/pjlib/include/pj/compat/os_auto.h.in
@@ -103,7 +103,7 @@
 /* Does the OS have socklen_t? */
 #undef PJ_HAS_SOCKLEN_T
 
-#if !defined(PJ_HAS_SOCKLEN_T) || PJ_HAS_SOCKLEN_T==0
+#if !defined(socklen_t) && (!defined(PJ_HAS_SOCKLEN_T) || PJ_HAS_SOCKLEN_T==0)
 # define PJ_HAS_SOCKLEN_T  1
   typedef int socklen_t;
 #endif