Added blitting
Fix: Referencing bug in ws_buffer methods
Add MIN() macro
Fix: size selection in ws_buffer_blit()

It previousely took the biggest sizes altough we should
take the smallest.
Fix: Use stride instead of width
Merge pull request #152 from TheNeikos/add-image_testing

Add image testing
Fix order of inclusions in surface.c
Merge pull request #154 from neithernut/fix-surface_inclusions

Fix order of inclusions in surface.c