Revert parts of "Fix the V4 valgrind integration"

Keep the MemoryManager as the pool argument of VALGRIND MEMPOOL
functions and access it through ExecutionEngine::memoryManager.

Change-Id: Iadb881ce8676088efe81870680aa75f6ba834248
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
rendercontrol example: calculate fbo size correctly

Change-Id: Ida1e7cb9426d31ed6406dd6db86f5834f0f1a6ac
Reviewed-by: Jørgen Lind <jorgen.lind@theqtcompany.com>