Android.mk: add ENABLE_SHARED flag

builds libwebp.so instead of libwebp.a
$ ndk-build ENABLE_SHARED=1

Change-Id: Ide05e3be4f9848852e6d7e9d99abe11344419241
Android.mk: move dwebp to examples/Android.mk

this depends on the top-level Android.mk for shared flags

Change-Id: Id418eb9639e839518a921ffcb6a376ce10aafbd2
examples/Android.mk: add cwebp

Change-Id: Id8edd3c17d82e4ab0087c315cd3ead1cb285e714
webpmux: warn when odd frame offsets are used

offsets are stored as (x/2, y/2)

Change-Id: Ic8f727ab7996a84c1f8c57f4f6dbaf8701bf8eae
Merge changes Id8edd3c1,Id418eb96,Ide05e3be

* changes:
  examples/Android.mk: add cwebp
  Android.mk: move dwebp to examples/Android.mk
  Android.mk: add ENABLE_SHARED flag
Merge "webpmux: warn when odd frame offsets are used"
QuantizeBlock SSE2 Optimization:

Another store to load forward block was detected coming from the function
FTransform.
FTransform save the output data 4 times 8 bytes each. when this data is
later being loaded by the QuantizeBlock function in one chunk of 16 bytes
that caused a store to load forward block.
The fix was done in the FTransform function where each two consecutive 8 bytes
were merged into one 16 bytes register and saved into the memory.
This fix gives ~21% function level gain and 1.6% user level gain.

Change-Id: Idc27c307d5083f3ebe206d3ca19059e5bd465992