scripts: Update warning list for gcc 4.9

Gcc 4.9 introduces a few extra warnings.  There are also stale
warnings in the list, so refresh it from doing an actual build, with
both the Android toolchain, as well as gcc 4.9.

Change-Id: I7240d24cf55792db304b06638209dc24fafcb0ae
Signed-off-by: David Brown <davidb@codeaurora.org>