Codestyle cleanup (mods.cpp, mapgen_math.cpp)

Fixes warnings mentioned in #1348 (except those in connection.cpp)
True it's three tabs here but doesn't change the basic issue I was pointing at. Code style suggests to keep file style too, so if everywhere else in this file it's changed to 1 tab it should be done here same way.
At least that's my opinion.
Of course the next line is affected too ;-)