Simplify Symbolizer::SymbolizePC() interface.

Return a linked list of AddressInfo objects, instead of using an array of
these objects as an output parameter. This simplifies the code in callers
of this function (especially TSan).

Fix a few memory leaks from internal allocator, when the returned
AddressInfo objects were not properly cleared.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@223145 91177308-0d34-0410-b5e6-96231b3b80d8