Fix EGL shim extension injection for GL ES 3 drivers.

The Android EGL shim injects GL_EXT_debug_marker into the ES driver
EXTENSIONS string for the OpenGL ES 1.x and 2.0/3.0/3.1 drivers if
the extension is not already provided. This feature is used by
GLES_trace.

In Open GL ES 3.0 it became possible to query an indexed version of
the EXTENSIONS string via GetStringi(). NUM_EXTENSIONS Gets were
also added to the specification (taken from Open GL).

If the shim does not have to inject the extension, then there is no
problem, as glGetString() and glGetStringi() / NUM_EXTENSIONS will
be consistent. However, if the Android EGL shim injects the
extension, NUM_EXTENSIONS and GetStringi() will report one less
extension than is really available.

Consistency between these methods is tested by the dEQP framework
with the dEQP-GLES3.functional.state_query.string.extensions test.
If the driver does not provide GL_EXT_debug_marker, this test
fails.

This change wraps all of the affected entry points so that the
wrapped driver extensions are never visible directly to dEQP,
eliminating the inconsistency.