[asan] Do not instrument special purpose LLVM sections.

Do not instrument globals that are placed in sections containing "__llvm"
in their name.

This fixes a bug in ASan / PGO interoperability. ASan interferes with LLVM's
PGO, which places its globals into a special section, which is memcpy-ed by
the linker as a whole. When those goals are instrumented, ASan's memcpy wrapper
reports an issue.

http://reviews.llvm.org/D10541

llvm-svn: 240723