During the Qt 4 -> 5 migration the setting of the extension flags
in QOpenGLFunctions/Extensions suffered a regression: flags like
GenerateMipmap were never set. This led to the unfortunate sitation
that features that were tied to these flags, like compressed texture
support or mipmap generation, got disabled.
This is now corrected by checking for the extensions like Qt 4 did.
Task-number: QTBUG-37588
Change-Id: I4a7beb1b435af11e05f5304aa04df2ec63b34c18
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
8adca56674