Fixes for QGIS 1.7.4:
1. providers/memory/memoryprovider.cpp
	Fix: 	- Correction to operate delete Features of layers managers
2. core/qgsvectorlayer.cpp
	Fixes: 	- Removal of displays optimization filter to avoid the hiding of displayed elements
		- Modification of events handling process during canvas refreshment in order to fix events scheduling errors
3. core/symbology-ng/qgsrendererv2.cpp
	Fix: - Implemetation of successive approximations to avoid external lines offset while zooming