build: fix distcheck

Now that distcheck no longer fails (see previous commit), let's
address the shortcomings.

* Makefile.am (CLEANDIRS, clean-local): New.
* doc/local.mk, examples/calc++/local.mk, examples/local.mk,
* examples/mfcalc/local.mk, examples/rpcalc/local.mk,
* src/local.mk
(CLEANDIRS): Get rid of Apple's *.dSYM directories.
(CLEANFILES): Get rid of *.output files.
* examples/variant-11.yy, examples/variant.yy: Don't generate
any of the auxiliary files (location.hh and the like).

examples/variant.yy

@@ -17,9 +17,9 @@
 
 %debug
 %language "c++"
-%defines
 %define api.token.constructor
 %define api.value.type variant
+%define api.location.file none
 %define parse.assert
 %locations