Add solution files for VC11/VS2012

added solution/project files for visual studio 2012. Note that these
differ from the 7.1 solution in the following ways:
*Disable Edit and continue (doesn't work with SafeSEH)
*Now links with the dll/debug dll version of the runtime (default in
2012)
*intermediate files are now written to a separate directory
*disable assembler output as it was causing builds to fail
intermittently