debug/dwarf: handle malformed line table with bad program offset

debug/dwarf: handle malformed line table with bad program offset

Touch up the line table reader to ensure that it can detect and reject
an invalid program offset field in the table header.

Fixes #53329.

Change-Id: Ia8d684e909af3aca3014b4a3d0dfd431e3f5a9f0
Reviewed-on: https://go-review.googlesource.com/c/go/+/413814
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>