Joseph Richey authored Jul 11, 2018 and Milan Broz committed Aug 07, 2018

Currently, AC_ARG_[ENABLE|WITH] are used in multiple different ways.
This change makes all their uses the same by following the style of
the GNU manual:
  - AC_ARG_ENABLE(foo) should only define $enable_foo
  - Use the 2 argument form with a --enable_foo flag
  - Use the 4 argument form with a --disable_foo flag
  - Format all uses the same way
  - Always compare using: test "x$enable_foo" = "xyes"

This makes the easier to debug, more readable, and shorter.

This formatting fix also revealed a bug (fix submitted seperately).