webos-image: Switch to non-GPLv3 version of gmp (v4.2.1)

:Release Notes:
Switch to using the non-GPLv3 version of gmp (v4.2.1).

:Detailed Notes:
Also, add patch to fix libpbnjson compilation error resulting from this
switch.

:Testing Performed:
Ran standard acceptance tests.

:QA Notes:

:Issues Addressed:
[GF-4063]  Remove GPLv3 components from webOS end-user images
[GF-52642] libpbnjson fails to build with non-GPLv3 version of gmp
           (v4.2.1)
[GF-52690] CCC: gmp=v4.3.1 gzip=v1.3.12

Open-webOS-DCO-1.0-Signed-off-by: Iyad Qumei <iyad.qumei@lge.com>
Change-Id: Iadc3093132d36b4cbf14019fc5291d60a9e49efe
Reviewed-on: https://g2g.palm.com/4035
Reviewed-by: DCO Verification
Reviewed-by: Iyad Qumei <iyad.qumei@lge.com>
Tested-by: Iyad Qumei <iyad.qumei@lge.com>
Tested-by: Kyungmin Lee <keimin.lee@lge.com>
Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Herb Kuta <herb.kuta@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>