Fix building problem with newer spandsp.

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@11540 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/applications/mod_fax/mod_fax.c

@@ -33,6 +33,8 @@
  */
 
 #include <switch.h>
+
+#define SPANDSP_EXPOSE_INTERNAL_STRUCTURES
 #include <spandsp.h>
 #include <spandsp/version.h>