Move the builtin headers to use the new license file header.

Summary:
These all had somewhat custom file headers with different text from the
ones I searched for previously, and so I missed them. Thanks to Hal and
Kristina and others who prompted me to fix this, and sorry it took so
long.

Reviewers: hfinkel

Subscribers: mcrosier, javed.absar, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D60406

llvm-svn: 357941