Move parts of llvm-symbolizer tool into LLVMSymbolize library.

Summary: See http://lists.llvm.org/pipermail/llvm-dev/2015-October/091624.html

Reviewers: echristo

Subscribers: llvm-commits, aizatsky

Differential Revision: http://reviews.llvm.org/D13998

llvm-svn: 251316