Change DynamicLoaderDarwinKernel::OSKextLoadedKextSummary to use

the Symbols::LocateExecutableObjectFile method to locate kexts and
kernels instead of copying them out of the memory of the remote
system.  This is the fix for <rdar://problem/12416384>.

Fix a variable shadowing problem in
Symbols::LocateMacOSXFilesUsingDebugSymbols which caused the symbol
rich executable binaries to not be found even if they were listed
in the dSYM Info.plist.

Change Symbols::DownloadObjectAndSymbolFile to ignore dsymForUUID's
negative cache - this is typically being called by the user and we
should try even if there's a incorrect entry in the negative cache.

llvm-svn: 165061