pirc does not build with C++

[plobsing]

Originally reported in parrot TT #1388 (http://trac.parrot.org/parrot/ticket/1388)

pirc does not build with C++

The problem is that C++ does not allow automatic conversions from int to enums. Some cases can be easily fixed with casting, but there is a lot of places where they are set via macros that hide the target type. Either that macros must be redesigned or the enums must be replaced by ints. Or change the build system to always compile it with C. Or anything that works.