Parallax mapping with slope information.
Overriding normal maps.

This reverts commit 362ef5f6.

Stack tracebacks couldn't be generated in LuaError::LuaError anyway and this
caused a second, empty traceback in most cases.  In cases where there wasn't
annother traceback the stack had already unwound and the traceback was empty.

This reverts commit 875f1327.
Fixed width format specifiers are only officially availale in C99 and C++11.

Looks like a bit of hasty copying and pasting from s_item.cpp.

Also fixes long-standing accuracy issue due to unknown wider
object count not being incremented.

Unless I'm mistaken, the chunk of code I'm moving there is potentially
executed hundreds of times inside the loop to get the exact same result
every time

Remove flagmask field from set_mapgen_params table
Add small bits of needed documentation