GLVersionNumber: Fix vendor version parser; Adapt to GlueGen commit 959d6d83ec26152343d538287c02eeebf0dcf238

Adapt to GlueGen commit 959d6d83ec26152343d538287c02eeebf0dcf238:
  - Use only RegExp and cache default (no wrapped whitespace tokenizer)
  - String match: Store end-of-match and flag defined components.
  - Remove manual parsing, utilize VersionNumber
  - No need to look further for 'updated' GL version, (probably the vendor version),
    since we utilize the ARB version number as set at creation.

Fix vendor version parser:
  - Cut off GL version part of versionString (fixes case where GL version was interpreted as vendor version)
  - Loop through remaining string until a valid version number w/ major.minor has been found