CFLAGS fix backported from devbranch.

CHANGELOG

@@ -6,6 +6,7 @@
 
 10302004 - Fixed a strcpy that should have been a strcat. (thanks, Tolga!)
            Removed .cvsignore files (we're in a Subversion repository, now).
+           Build system respects external CFLAGS now. (thanks, Adam!)
 09212003 - Happy September. Fixes to bootstrap on MacOS X. Seeking now tries
            to respect pre-buffered data.
 

configure.in

@@ -493,7 +493,7 @@ AC_CHECK_FUNCS([memset strrchr])
 
 AC_CHECK_SIZEOF(int, 4)
 
-CFLAGS="$CFLAGS $PHYSFSCFLAGS -D_REENTRANT -D_THREAD_SAFE"
+CFLAGS="$PHYSFSCFLAGS $CFLAGS -D_REENTRANT -D_THREAD_SAFE"
 LDFLAGS="$LDFLAGS $PHYSFSLDFLAGS -no-undefined"
 
 dnl Add Makefile conditionals