Mesh: Fixed normalShadowmap.fs's compile error in GeForce cards.

Radeon HD 6870 permits vectors to compare to 0 (although the result is
unclear), while GeForce 650M fails to compile the source.
surface: Refactored WarMap's traceHit method interface.

It used to be similar to Entity::traceHit(), but I feel it's better
to write it in more object oriented manner.  Namely, input values
and output values are structurized to be less cluttering and
more extensive.  This is effective for traceHit() because it tend
to have many arguments for both inputs and outputs.
surface: Make Aerial AI avoid crashing on ground (SurfaceCS).

It detects the ground terrain by tracing rays and try to avoid it.
It won't always succeed, but it's now way harder to crash when
auto pilot is enabled.

This commit looks chaniging much of Aerial.cpp, but actually most of
the commit is reordering of codes.
Mesh: Fix texture coordinate is inverted in Y direction.