`make tags` fixes (GH-717)

* Fix `make tags` warnings

`make tags` target tries to find C sources and headers in "Grammar" and
"Mac" folders and generates these warnings:

    ctags: Warning: cannot open source file "Grammar/*.[ch]" : No such file or directory
    ctags: Warning: cannot open source file "Mac/*.[ch]" : No such file or directory

This commit changes $SRCDIRS variable in configure.ac to remote these
directories. This variable is used only for tags generation.

Also, "configure" was regenerated with `autoreconf`.

* Fix `make tags` fail on non-default tag names

When ctags overrides default tags filename (e.g. `-f .tags`) `make tags`
is failed because it assumes to see default `tags` filename:

    sort: cannot read: tags: No such file or directory

This commit explicitly specifies "tags" filename for tags generation.
diff --git a/configure.ac b/configure.ac
index aca8255..8ab1c03 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5200,7 +5200,7 @@
 done
 
 AC_SUBST(SRCDIRS)
-SRCDIRS="Parser Grammar Objects Python Modules Mac Programs"
+SRCDIRS="Parser Objects Python Modules Programs"
 AC_MSG_CHECKING(for build directories)
 for dir in $SRCDIRS; do
     if test ! -d $dir; then