firefox: Perform a number of cleanups and fix consistency issues.

firefox: Perform a number of cleanups and fix consistency issues.

- parallel builds need to happen via MOZ_MAKE_FLAGS and it gripes if still
  passed -jN, so keep the old value before we clear it.
- Move the HOST_LIBIDL stuff into configure, otherwise bad things happen when
  you don't have pkg-config on the build host.
- Prior to 3.6, wireless-tools can be, or not be built already and the Necko
  wifi options deals.  With how 3.6 is configured, it must be disabled or
  DEPENDED on.  For consistency, turn it off.
- In 3.5 and newer, libnotify can be used, add it to DEPENDS (could be
  disabled).
- Because of both of the above, bump PR.

Signed-off-by: Tom Rini <tom_rini@mentor.com>
Acked-by: Khem Raj <raj.khem@gmail.com>