muxedit: silence some uninitialized warnings

src/mux/muxedit.c:490: warning: 'x_offset' may be used uninitialized in this function
src/mux/muxedit.c:490: warning: 'y_offset' may be used uninitialized in this function

Change-Id: I4fd27f717e59a556354d0560b633d0edafe7a4d8
(cherry picked from commit 14cd5c6c401fd769995030c135d07fae56f2ecca)
wicdec: silence a format warning

from x86_64-w64-mingw32-gcc

examples/wicdec.c: In function ‘ExtractICCP’:
examples/wicdec.c:131:21: warning: format ‘%u’ expects argument of type
‘unsigned int’, but argument 4 has type ‘size_t’ [-Wformat]

Change-Id: I6642dae62265a2276ae9ac96dd8ce6f1e2d37ca5
(cherry picked from commit ffae9f31e80ed7344987b24b21af831806fa2e69)
Regression fix for alpha channels using color cache:

Considering the fact that insert to/lookup from the color cache is always 32
bit, use DecodeImageData() variant in that case.

Conflicts:
	src/dec/vp8l.c

Change-Id: I6c665a6cfbd9bd10651c1e82fa54e687cbd54a2b
(cherry picked from commit a37eff47d6b6f0a3721a9710235cd894c2982e9b)
update ChangeLog

Change-Id: Idea3464bbcb28896179c99488e7b96a4341b508a