nm: Explicitly print weak 'V' or 'T' and common 'C' symbols.

nm: Explicitly print weak 'V' or 'T' and common 'C' symbols.

Mimic binutils nm for bsd and posix formats which uses 'V' for weak
symbols, 'C' for common symbols and 'T' for weak functions. Also fix
some formatting issues. Don't print undefined addresses as zeros, but
make sure there is enough padding instead. Just print UNIQUE for
GNU_UNIQUE to make it fit 6 chars, like other binding names in sysv
format.

https://sourceware.org/bugzilla/show_bug.cgi?id=25227

Signed-off-by: Mark Wielaard <mark@klomp.org>