get to clean compile under vs2012

Added some missing (but existing in branch) files to libzmq11 project needed
to compile as static library by VS2012 (at least), and fixed some warnings.
One warning remains in raw_decoder.cpp, which I'm leaving for now because I'm
not sure how project owners would like to fix it.
Merge pull request #633 from eburkitt/vs2012-clean-compile

get to clean compile under vs2012