Breakpad uses x86 as the architecture name, not i386

Breakpad uses x86 as the architecture name, not i386. Most tools don't care
what architecture name is shown in a symbol file's MODULE line, but the Mac
crash_report tool's on_demand_symbol_supplier does. The new Mac dumper
inadvertently used i386. Correct that to make it x86. Temporarily make the
on_demand_symbol_supplier accept symbol files whose architecture is i386.
Also add x86_64 to the set of architectures that the on_demand_symbol_supplier
considers valid.

BUG=none
TEST=none

Committed: http://code.google.com/p/google-breakpad/source/detail?r=638

[Mark Mentovai]

Neal, I’ll check this in as-is and then immediately check in a followup to
remove i386 from on_demand_symbol_supplier. I want to do it this way so that we
have a revision checked in where QA can build crash_report and have something
that accepts the broken symbol files that list i386.

[mochalatte]

LGTM