[UBSan] Allow UBSan location to store frames returned by symbolizer.

Summary:
__ubsan::getFunctionLocation() used to issue a call to symbolizer, and
convert the result (SymbolizedStack) to one of UBSan structures:
SourceLocation, ModuleLocation or MemoryLocation. This:
(1) is inefficient: we do an extra allocation/deallocation to copy data,
while we can instead can just pass SymbolizedStack around (which
contains all the necessary data).
(2) leaks memory: strings stored in SourceLocation/MemoryLocation are
never deallocated, and Filipe Cabecinhas suggests this causes crashes
of UBSan-ified programs in the wild.

Instead, let Location store a pointer to SymbolizedStack object, and
make sure it's properly deallocated when UBSan handler exits.

ModuleLocation is made obsolete by this change, and is deleted.

Test Plan: check-ubsan test suite

Reviewers: rsmith, filcab

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D7548

llvm-svn: 228869