Update several administrative files mainly to facilitate releasing.

Update several administrative files mainly to facilitate releasing.

* HACKING (Administrivia): Make the git-merge-changelog notes more
helpful.
(Test suite): Don't say lalr1.cc is not exercised in the test suite.
(Release Procedure): Update for git and add numerous details that were
previously missing.
* Makefile.am (EXTRA_DIST): Remove Makefile.cfg and Makefile.maint.
* maint.mk (announcement): Don't list bison as a bootstrap tool so
that announcements don't claim we bootstrapped with whatever bison
happened to be in PATH.  Add flex as a bootstrap tool.
* Makefile.maint: Remove, previously replaced by maint.mk.
* Makefile.cfg: Remove, and migrate settings to...
* cfg.mk: ... here for the sake of `make announcement'.
* bootstrap.conf (gnulib_modules): Add announce-gen.
* README: Say GNU Bison instead of just Bison.  Suggested by Karl
Berry.