[PATCH] return absolute paths from Parrot_locate_runtime_file

[Jeff Horwitz]

Parrot_readbc can segfault when loading an absolute path to a file (in my
case, only under GDB). the problem lies in Parrot_locate_runtime_file,
and is similar to the one in ticket #32087.

the attached patch adds a check in Parrot_locate_runtime_file so it
returns absolute paths as is. it handles win32 paths (and drive letters)
as well. hopefully i chose the most logical place for this -- i didn't
think it belonged in Parrot_readbc itself.

-jeff