Assert define fix.

CHANGELOG

@@ -8,7 +8,7 @@
            1.2.3, which properly includes the security fix. Fixed "make dist"
            to handle .svn dirs and other file changes. Removed "debian"
            directory. Fixed warning in physfs.c. Updated CWProjects.sit.
-           Upped version to 1.0.1.
+           Assert define fix. Upped version to 1.0.1.
 07132005 - Moved to zlib122, and security fix discussed here:
            http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-2096
 06122005 - Added support for mingw to Unix build process (thanks, Matze!).

physfs_internal.h

@@ -18,7 +18,7 @@
 
 #ifdef HAVE_ASSERT_H
 #include <assert.h>
-#else
+#elif (!defined assert)
 #define assert(x)
 #endif