ftmod_misdn: Add -D_BSD_SOURCE to get u_int and friends.

Needed for the mISDN/mISDNif.h header structs, linux/types.h only
provides them for kernel code:

In file included from src/ftmod/ftmod_misdn/ftmod_misdn.c:51:
/usr/include/mISDN/mISDNif.h:296: error: expected specifier-qualifier-list before 'u_int'
/usr/include/mISDN/mISDNif.h:306: error: expected specifier-qualifier-list before 'u_int'
/usr/include/mISDN/mISDNif.h:339: error: expected ')' before 'nr'
...
Signed-off-by: Stefan Knoblich <stkn@openisdn.net>

libs/freetdm/Makefile.am

@@ -251,7 +251,7 @@ endif
 if HAVE_MISDN
 mod_LTLIBRARIES += ftmod_misdn.la
 ftmod_misdn_la_SOURCES  = $(SRC)/ftmod/ftmod_misdn/ftmod_misdn.c
-ftmod_misdn_la_CFLAGS   = $(FTDM_CFLAGS) $(AM_CFLAGS) $(MISDN_CFLAGS)
+ftmod_misdn_la_CFLAGS   = $(FTDM_CFLAGS) $(AM_CFLAGS) $(MISDN_CFLAGS) -D_BSD_SOURCE
 ftmod_misdn_la_LDFLAGS  = -shared -module -avoid-version
 ftmod_misdn_la_LIBADD   = libfreetdm.la
 endif