add cscope/ctags make targets

Newcomers to the code often use these tools to learn their way around.
Integrate them into the build so that we don't accidentally track their
files.

Signed-off-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>

.gitignore

@@ -10,6 +10,8 @@ config.h
 config.log
 Makefile
 Makefile.in
+cscope.out
+tags
 .deps
 stamp-h1
 *.o

Makefile.am

@@ -4,3 +4,10 @@ SUBDIRS = gl libopts src doc
 
 ACLOCAL_AMFLAGS = -I gl/m4 -I libopts/m4 -I m4
 
+ctags:
+	find . -type f -name "*.[ch]*" | xargs @CTAGS@
+
+cscope:
+	@CSCOPE@ -b -R
+
+cref: ctags cscope

configure.ac

@@ -15,6 +15,8 @@ AM_PROG_CC_C_O
 if [ test "$GCC" = "yes" ];then
 	CFLAGS="$CFLAGS -Wall"
 fi
+AC_PATH_PROG(CTAGS, ctags, /bin/true)
+AC_PATH_PROG(CSCOPE, cscope, /bin/true)
 
 AC_CHECK_SIZEOF([unsigned long])
 AC_C_BIGENDIAN