* Changes the compatbility matrix version to 5.0 & marks optional
* Tweaks the interface name in case it doesn't get removed soon
(otherwise readme looks silly)
* Adds a README.md to mapper/stable-c
* Adds VTS test to validate versions match
Test: build + mapper VTS
Change-Id: I9b1256e07aaf2876d579a5487d2051c60097fb70
Specifically include the header encoding. Initially
omitted as it's a bit redundant, the value in having
bit-for-bit identical encoding between gralloc4 &
imapper5 seems worthwhile enough to keep it.
Test: impltests + VtsHalGraphicsMapperStableC
Change-Id: Iee37bb97acf40362c301a06f9118938b1a0c2cd9