gdb: remove context_stack::static_link

I don't think it's needed to record this information in the
context_stack structure.  The only user is the DWARF reader, where it
can very well be a local variable.

Change-Id: I6e33affbf03f11c0d0ab60067f169137fde1c994
Approved-By: Tom Tromey <tom@tromey.com>
2 files changed