This commit adds the glue code necessary to integrate the
SymbolFileBreakpad into the plugin system. Most of the methods are
stubbed out. The only method implemented method is AddSymbols, which
parses the PUBLIC "section" of the breakpad "object file", and fills out
the Module's symtab.
To enable testing this, I've made two additional changes:
- dump Symtab from the SymbolVendor class. The symtab was already being dumped as a part of the object file dump, but that happened before symbol vendor kicked in, so it did not reflect any symbols added there.
- add ability to explicitly specify the external symbol file in lldb-test (so that the object file could be linked with the breakpad symbol file). To make things simpler, I've changed lldb-test from consuming multiple inputs (and dumping their symbols) to having it just process a single file per invocation. This was not a problem since everyone was using it that way already.