Math: added convenience function Vector::resized().
Math: don't include <algorithm> in header file.

31ce072f39513277a70d1d3611814cdc0a261635 was wrong, this header is
harmful. This beast includes ~46k LOC, much more than <*stream> class of
headers. Rewritten min() and max() manually, which surprisingly leads to
shorter implementation than previously. Compilation time on my machine
reduced from ~4:30 to ~4:21, not bad.