Initial libmediaformatshaper

mediaformatshaper library to amend MediaFormat parameters before
encoding. This is the initial cut of the library.
Disabled by default, enable with "setprop debug.stagefright.enableshaping 1"

Bug: 182827840
Test: build, boot, encode video
Change-Id: I8cefb6ed6ad286ae2192796bf15760e873e0d2f3