Added invalid pch warning when compiling under C::B/MingW.
Moved video debug info in front and add a check preventing pop/pushing context state there.
Spotted two glEnable/Disable calls that could be checked first.
Fixed a comment while seeing it.
Added pathfinding and way point support to enemy sprites.

Enemy sprites will now use path finding to walk and locate the character.

This feature is for me working so far with one rough edge I need to deal with soon:

When behind an obstacle, the enemy sprite will make heavy computation to try and
catch you uselessly. I need then to be able to specify an optional limit in the close list
of path nodes. I'll do that in another commit.
Added missing enemies in the maps and made use of the new waypoint feature.