TypeSystem is now a plugin interface and removed any "ClangASTContext...

TypeSystem is now a plugin interface and removed any "ClangASTContext &Class::GetClangASTContext()" functions.

This cleans up type systems to be more pluggable. Prior to this we had issues:
- Module, SymbolFile, and many others has "ClangASTContext &GetClangASTContext()" functions. All have been switched over to use "TypeSystem *GetTypeSystemForLanguage()"
- Cleaned up any places that were using the GetClangASTContext() functions to use TypeSystem
- Cleaned up Module so that it no longer has dedicated type system member variables:
    lldb::ClangASTContextUP     m_ast;          ///< The Clang AST context for this module.
    lldb::GoASTContextUP        m_go_ast;       ///< The Go AST context for this module.
    
    Now we have a type system map:
    
    typedef std::map<lldb::LanguageType, lldb::TypeSystemSP> TypeSystemMap;
    TypeSystemMap               m_type_system_map;    ///< A map of any type systems associated with this module
- Many places in code were using ClangASTContext static functions to place with CompilerType objects and add modifiers (const, volatile, restrict) and to make typedefs, L and R value references and more. These have been made into CompilerType functions that are abstract:

    class CompilerType
    {
    ...
    
    //----------------------------------------------------------------------
    // Return a new CompilerType that is a L value reference to this type if
    // this type is valid and the type system supports L value references,
    // else return an invalid type.
    //----------------------------------------------------------------------
    CompilerType
    GetLValueReferenceType () const;

    //----------------------------------------------------------------------
    // Return a new CompilerType that is a R value reference to this type if
    // this type is valid and the type system supports R value references,
    // else return an invalid type.
    //----------------------------------------------------------------------
    CompilerType
    GetRValueReferenceType () const;

    //----------------------------------------------------------------------
    // Return a new CompilerType adds a const modifier to this type if
    // this type is valid and the type system supports const modifiers,
    // else return an invalid type.
    //----------------------------------------------------------------------
    CompilerType
    AddConstModifier () const;

    //----------------------------------------------------------------------
    // Return a new CompilerType adds a volatile modifier to this type if
    // this type is valid and the type system supports volatile modifiers,
    // else return an invalid type.
    //----------------------------------------------------------------------
    CompilerType
    AddVolatileModifier () const;

    //----------------------------------------------------------------------
    // Return a new CompilerType adds a restrict modifier to this type if
    // this type is valid and the type system supports restrict modifiers,
    // else return an invalid type.
    //----------------------------------------------------------------------
    CompilerType
    AddRestrictModifier () const;

    //----------------------------------------------------------------------
    // Create a typedef to this type using "name" as the name of the typedef
    // this type is valid and the type system supports typedefs, else return
    // an invalid type.
    //----------------------------------------------------------------------
    CompilerType
    CreateTypedef (const char *name, const CompilerDeclContext &decl_ctx) const;
    
    };
    
Other changes include:
- Removed "CompilerType TypeSystem::GetIntTypeFromBitSize(...)" and CompilerType TypeSystem::GetFloatTypeFromBitSize(...) and replaced it with "CompilerType TypeSystem::GetBuiltinTypeForEncodingAndBitSize(lldb::Encoding encoding, size_t bit_size);"
- Fixed code in Type.h to not request the full type for a type for no good reason, just request the forward type and let the type expand as needed

llvm-svn: 247953