Remainder of the C99 decltests.

Maketest.py grew several new features, notably:

 - macros expanding to string literals
 - arbitrary expressions in function-like macro calls
   (this doesn't work for true functions, because we want to know
    the argument type)
 - includes= in preamble == "this header is supposed to include
   that other header" (i.e. "repeat all the tests for that other
   header, here")