<rdar://problem/13854277>
<rdar://problem/13594769>

Main changes in this patch include:
- cleanup plug-in interface and use ConstStrings for plug-in names
- Modfiied the BSD Archive plug-in to be able to pick out the correct .o file when .a files contain multiple .o files with the same name by using the timestamp
- Modified SymbolFileDWARFDebugMap to properly verify the timestamp on .o files it loads to ensure we don't load updated .o files and cause problems when debugging

The plug-in interface changes:

Modified the lldb_private::PluginInterface class that all plug-ins inherit from:

Changed:

virtual const char * GetPluginName() = 0;

To:

virtual ConstString GetPluginName() = 0;

Removed:

virtual const char * GetShortPluginName() = 0;

- Fixed up all plug-in to adhere to the new interface and to return lldb_private::ConstString values for the plug-in names.
- Fixed all plug-ins to return simple names with no prefixes. Some plug-ins had prefixes and most ones didn't, so now they all don't have prefixed names, just simple names like "linux", "gdb-remote", etc.