Symbolize: Make DWPName a symbolizer option instead of an argument to symbolize{,Inlined}Code.

This makes the interface simpler and more consistent with the interface for
.dSYM files and fixes a bug where llvm-symbolizer would not read the dwp if
it was asked to symbolize data before symbolizing code.

Differential Revision: https://reviews.llvm.org/D63114

llvm-svn: 363025