Fixed|Line: Avoid conversion to integer

de::floor returns an integer while std::floor returns a floating
point type. Here a coord_t was expected.
Debug|Hexen: Signed vs. unsigned integers
Fixed|Partitioner: Compiler error (global variable shadowing)

The static validCount in partitioner.cpp was shadowed by the global
variable of the same name, with C-linkage, in render/r_main.h when
building with MSVC (at least). Resulting in holes around one-way
window hack constructs in some maps.