drsyms does not look in /usr/lib/debug/.build-id/ directory for symbol files

There is a new scheme for storing separate debug info: for build id 0xabcdef.debug, the file is stored in /usr/lib/debug/.build-id/ab/cdef.debug and the debuglink section says "cdef.debug". We should augment drsym's current /usr/lib/debug search scheme to include this.