[boost] mingw-3.4.2 release candidate and regression tests

Hello I'm going to upgrade testing environment from mingw-3.4.1 to mingw-3.4.2 release candidate (I will keep running tests on mingw-3.3.1 with toolset mingw, as it is now). I'm also going to upgrade mingw-runtime to version 3.5 and w32api to version 3.1. This might of course change results of regression tests I'm running, but I believe that these results will be closer to release version of mingw 3.4.2, when it's finally released. Any objections, opinions or advices about this move? B.