[compiler-rt] Add SourceLocations for float_cast_overflow data.

Summary:
Compiler-rt part of http://reviews.llvm.org/D11757
I ended up making UBSan work with both the old version and the new
version of the float_cast_overflow data (instead of just erroring with
the previous version). The old version will try to symbolize its caller.

Now we compile the float_cast_overflow tests without -g, and make sure
we have the source file+line+column.

If you think I'm trying too hard to make sure we can still use both
versions, let me know.

Reviewers: samsonov, rsmith

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11793

llvm-svn: 244567