Add additional generated files to .gitignore.
Allow maintainer mode to be disabled (debian build scripts do this).
Add ZLIB_CFLAGS to CFLAGS.
Add file config.h.in~ to .gitignore.
Fix hyphen-used-as-minus-sign lintian warnings by escaping -.

From Debian patch from Bas Couwenberg <sebastic@xs4all.nl>.
Fix spelling-error-in-manpage by using 'allows one to'.

Author: Bas Couwenberg <sebastic@xs4all.nl> via Debian patch.
Merge pull request #140 from joto/master

Various cleanups