Change the 'make' rules for *_lex.c, *_yacc.c, and *_comp.h to put
the end files names into whatever #line directives that refer to
the generated names (lex.yy.c, y.tab.c, y.tab.h). This should not
produce any change in behavior during compilation except to provide
more accurate specifications of where any warnings or errors occur.
Add a 'make dist' target that copies generated scanner and parser
files to sys/share. (As mentioned in the previous patch, I haven't
committed any of those since I have different versions of flex and
also of bison.)