GCC 4.9.4 was already used for MIPS and all hosted targets; this enables
it across the board for everything (ie m68k and arm native)
Other changes:
* Use '-Os' as the default optiomization for all targets
(was only disabled for arm native)
* Enable -funit-at-a-time and -Wextra
* Drop all obsolete toolchain patches
* Update ARM multilib/exception patch
* Bump toolchain libs (gmp, mpfr, mpc) to recommended versions, and
add 'isl' to enable better optimization & vectorization opportunities.
(Will revisit optimization for the codecs and plugins at a later date)
Confirmed working:
* armv4t (ipodmini2g and many other PP502x targets)
* arm >= v5 (sansaclipplus, ipod6g, ipodnano2g, sansafuzeplus)
* m68k (ihp100)
Change-Id: If9ed405ae0f289d9adea46d4cf46bfefc2f4250d
