(EXTRA_DIST): Add decl.m4, error.m4, mbstate_t.m4, prereq.m4.

Remove signedchar.m4.

m4/Makefile.am

@@ -4,6 +4,8 @@ EXTRA_DIST = \
 c-bs-a.m4 \
 ccstdc.m4 \
 d-ino.m4 \
+decl.m4 \
+error.m4 \
 fnmatch.m4 \
 getline.m4 \
 gettext.m4 \
@@ -13,10 +15,11 @@ jm-mktime.m4 \
 largefile.m4 \
 lcmessage.m4 \
 malloc.m4 \
+mbstate_t.m4 \
 mktime.m4 \
+prereq.m4 \
 progtest.m4 \
 realloc.m4 \
-signedchar.m4 \
 uintmax_t.m4 \
 ulonglong.m4 \
 utimbuf.m4 \