Disable webp also for ios

Already disabled for android and winrt; seems that libwebp's use of
neon does not compile.

Change-Id: Ia119244da1ae3c92f69dfe5ed91d20e665102958
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
Avoid implicit function declaration compile errors in libjasper

Compilation for macx-ios-clang_OSX_10.9 would fail since the
jas_eprintf function was used undeclared. Fix by #including
jas_debug.h before4 use of that function.

Also restructure some code in jpc_tsfb.c to prevent the same
issue for jpc_tsfb_synthesize2 and jpc_tsfb_analyze2.

Change-Id: Ib5b444873af6aa756d1c77145acdd863eaca0bd2
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>