Remove some dead code from buildsym.c

This patch removes some code from buildsym.c that, according to the
comment, was only used for some SCO or maybe COFF thing.  This code is
dead now, and it was a hack anyway and probably should never have been
allowed.

In v2 I've removed the entire block, since callers should be pairing
pushes and pops anyway.

Approved-By: Simon Marchi <simon.marchi@efficios.com>