a bit of refactoring
A bit more refactoring. Changed name from "CPP11" to "C" throughout, for better consistency with the litmus tool. Working on C parser, getting it to accept parameters, and be closer to actual C code. Added a few more litmus tests. Moved CAst module from litmus into lib, so that Herd can use it too; same for RunType. Adjusted litmus a little bit, so that it accepts the newly-extended "pseudo" type. I also made the CAst.t type parametric in the type of the body. For litmus, the body of each procedure is uninterpreted, so the type is "string CAst.t". For herd, the body is interpreted as a list of pseudo-instructions, so the type is "(pseudo list) CAst.t".