Small Patch and VS2005 enum pb

Hi,

A small patch for adding:
- a missing include <string> in a header
- a missing file ASTConsumer.cpp in clangAST projet for VS

This allow to compile on VS2005 but there is still the old problem that enum
are signed by default on VS2005. This cause clang to assert on code like

Struct A { int I; }; struct A a;

More specifically, the problem is in DeclSpec.h at the line 64 and 111 and
174:

miniclang.patch (1.05 KB)