[Sema] Store a SourceRange for multi-token builtin types

Summary:
clang-tidy's modernize-use-auto check uses the SourceRange of a
TypeLoc when replacing the type with auto.
This was producing the wrong result for multi-token builtin types
like long long:

-long long *ll = new long long();
+auto long *ll = new long long();

Reviewers: alexfh, hokein, rsmith, Prazek, aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D25363

llvm-svn: 284885