PlatformDarwinKernel maintains a list of kexts and kernels

that it finds on the local computer in "well known" locations
when we start up the darwin-kernel platform.  It did not 
distinguish between kexts/kernels with dSYMs from others -
when it needed a kernel/kext with a given UUID, it would grab
the first one it finds.

This change separates these into two vectors -- a collection
of kexts and kernels with dSYMs next t othem, and a collection
of kexts and kernels without dSYMs.  When we have a bundle ID
and uuid to search for, we first try the collections with
dSYMs, and if that fails, then we try the collections that
did not have dSYMs next to them.

Often times we'll have a situation where a kext will be 
installed in multiple locations on a system, but only one
of them will have a dSYM next to it, where the dev just copied
it to a local directory.  This fixes that problem, giving
precedence to those binaries with debug information.

llvm-svn: 277123