-Add templated functions for arbitrary fixed-point multiplication and division. These replace FixedMulXX and FixedDivXX functions.
-Add a function R_ProjectSeg to translate a seg_t's vertices to camera coordinates and project it into screen columns, calculating texture-mapping intial and step values and saving them into a drawseg_t.

git-svn-id: http://odamex.net/svn/root/branches/texmanager@4363 b0bcef46-2027-0410-bd56-ab726e9a1d04
-Add a template class fixed_generic_t to represent a fixed-point number with a given number of bits of precision. Convenient typedefs are included, such as fixed16_t, fixed17_t, etc.
-Provide templated versions of FixedMul and FixedDiv that take a template parameter to specifiy the bits of precision of the result.
-Decrease the precision of drawseg_t::invz1 & 2 to reduce overflows when walking underneath an opening.
-Remove seg_t::offset since side_t::textureoffset is used instead.
-Remove seg_t::length since it is unused.

git-svn-id: http://odamex.net/svn/root/branches/texmanager@4364 b0bcef46-2027-0410-bd56-ab726e9a1d04