Run cmparseMSBuildXML.py on cl.xml, lib.xml, and link.xml to generate
our flag tables:

 python cmparseMSBuildXML.py -x ".../MSBuild/Microsoft.Cpp/v4.0/v120/1033/cl.xml" > cmVS12CLFlagTable.h
 python cmparseMSBuildXML.py -x ".../MSBuild/Microsoft.Cpp/v4.0/v120/1033/lib.xml" > cmVS12LibFlagTable.h
 python cmparseMSBuildXML.py -x ".../MSBuild/Microsoft.Cpp/v4.0/v120/1033/link.xml" > cmVS12LinkFlagTable.h

Fix up the declaration names at the top of each file.  Finally, teach
cmVisualStudio10TargetGenerator to select the version of the table
matching the version of VS.