libcopybit: do not use GNU old-style field designators

Summary: Not using a GNU extension improves portability

Test Plan: verfied

Reviewers: randall.rushing, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D660
libgralloc & libhwcomposer: do not use GNU old-style field designators

Summary:
Avoiding the use of gnu extensions improves code portability.
Somehow I had this locally, then missed it on my first pass of this repo.

Test Plan: verified.

Reviewers: synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D13