Many bug fixes etc.

Many bug fixes etc.
- Apply a fix for the "thundering herd" problem when using "-j -l".
  This also fixes bug #4693.
- Fix bug #7257: allow functions as ifdef arguments
- Fix bug #4518: make sure we print all double-colon rules with -p.
- Upgrade to autconf 2.58/automake 1.8/gettext 0.13.1
- Various doc cleanups, etc.