Switch from custom assert() to libc assert() in mach/proto/as.
Continue to disable asserts if DEBUG == 0.
This change found a problem in the build system; comm2.y was missing
depedencies on comm0.h and comm1.h. Add the missing dependencies to
the cppfile rule. Allow the dependencies by modifying cppfile in
first/build.lua to act like cfile if t.dir is false.
Now that comm2.y gets rebuilt, I must fix the wrong prototype of
yyparse() in comm1.h.
I got unlucky as induo() in comm5.c was reading beyond the end of the
array. It found an operator "= " ('=' then space) in the garbage, so
it returned a garbage token number, and "VAR = 123" became a syntax
error. Unbreak induo() by terminating the array.
