resolve an automake warning about subdirs on latest automake

The file 'libs/sofia-sip/s2check/exit77.c' was moved in order to
silence the warning and to keep the build working. There might be a
build problem that results from this file move, but after serveral
build tests I have not found one. The contents of the file are
specifically for the make check target, so I believe it would be
highly unlikely to cause problems with any production feature.

FS-7122 #resolve

libs/sofia-sip/.update

-Wed Jan  7 17:18:14 CST 2015
+Wed Jan  7 11:24:56 PST 2015

libs/sofia-sip/libsofia-sip-ua/nta/Makefile.am

@@ -76,7 +76,7 @@ check_nta_SOURCES =	check_nta.c check_nta.h \
 check_nta_LDADD = 	${LDADD} @CHECK_LIBS@
 
 else
-check_nta_SOURCES = 	$(top_srcdir)/s2check/exit77.c
+check_nta_SOURCES = 	exit77.c
 endif
 
 # ----------------------------------------------------------------------

libs/sofia-sip/s2check/Makefile.am

@@ -30,7 +30,7 @@ libs2_a_SOURCES = 	s2check.h s2tcase.c \
 # ----------------------------------------------------------------------
 # Install and distribution rules
 
-EXTRA_DIST =		exit77.c
+EXTRA_DIST =
 
 # ----------------------------------------------------------------------
 # Tests