Apparently using std::vector::push_back causes heavy inlining in MSVS.
This refactor (no functionality change) reduces the binary size from
~10kb for all the gl::Determine* functions plus the holding function
(setTextureExtensionSupport) to about 1.4k.

The visible size of my compiled 32-bit Release libGLESv2.dll went from
4648 to 4642 kb.

Note that using PoD arrays was sinificantly better than using vectors
with initializer lists (size was ~4kb instead vs 1.4kb).

BUG=angleproject:2022

Change-Id: I5b7efd41455d5ee35afc699bafef31ce8367934e
Reviewed-on: https://chromium-review.googlesource.com/493890Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>