Added the ability for clients to grab a set of symbol table indexes and then

add them to a fast lookup map. lldb_private::Symtab now export the following
public typedefs:

namespace lldb_private {

	class Symtab {
		typedef std::vector<uint32_t> IndexCollection;
		typedef UniqueCStringMap<uint32_t> NameToIndexMap;
	};
}

Clients can then find symbols by name and or type and end up with a 
Symtab::IndexCollection that is filled with indexes. These indexes can then
be put into a name to index lookup map and control if the mangled and 
demangled names get added to the map:

bool add_demangled = true;
bool add_mangled = true;
Symtab::NameToIndexMap name_to_index;
symtab->AppendSymbolNamesToMap (indexes, add_demangled, add_mangled, name_to_index).

This can be repeated as many times as needed to get a lookup table that
you are happy with, and then this can be sorted:

name_to_index.Sort();

Now name lookups can be done using a subset of the symbols you extracted from
the symbol table. This is currently being used to extract objective C types
from object files when there is no debug info in SymbolFileSymtab.

Cleaned up how the objective C types were being vended to be more efficient
and fixed some errors in the regular expression that was being used.

llvm-svn: 145777