SF: Compile with -Wextra

Compile with -Wextra for additional conversion checks. In each file
which produces compile errors -Wextra is ignored.

Bug: 175126758
Test: m surfaceflinger && m libsurfaceflinger_unittest
Change-Id: Iec6bcc699715a99c8c65d891ab3c0481e884c728
52 files changed