[analyzer] Sort path diagnostics with array_pod_sort.
They're expensive to compare and we won't sort many of them so std::sort
doesn't give any benefits and causes code bloat. Func fact: clang -O3 didn't
even bother to inline libc++'s std::sort here.
While there validate the predicate a bit harder, the sort is unstable and we
don't want to introduce any non-determinism. I had to spell out the function
pointer type because GCC 4.7 still fails to convert the lambda to a function
pointer :(
No intended functionality change.
llvm-svn: 232263