Make c89(1) invoke /usr/bin/cc with argv[0] also set to /usr/bin/cc,
similar to what c99(1) does, to prevent "c89: illegal option -- 1"
messages, when clang is /usr/bin/cc.

Reported by:	tijl
MFC after:	3 days
Make c99(1) invoke /usr/bin/cc with argv[0] set to "/usr/bin/cc" instead
of just "cc", since there is no reason to cause additional path searches
in this case.

MFC after:	3 days
Make ctfconvert work correctly on clang-compiled object files.  Clang
puts the full original source filename in the STT_FILE entry of the ELF
symbol table, while gcc saves only the basename.

Since the DWARF DW_AT_name attribute contains the full source filename,
both for clang and gcc, ctfconvert takes just the basename of it, for
matching with the STT_FILE entry.  So when attempting to match with such
an entry, use its basename, if necessary.

Reported by:	avg
MFC after:	1 week