gccld.cpp:

 Fix typo in header.
 Add IsArchive static method.
 Roll LoadLibraryFromDirectory() into LoadLibrary(), and factor
  LoadLibraryExactName() out of the result. Instead of treating the current
  directory specially, just insert it into LibPaths in the beginning of
  main().
 Make LoadLibrary() take a "search" flag that says whether to search for the
  correct library, or just trust that LibName is right.
 Make LinkLibrary() take a "search" flag, and pass it to LoadLibrary().
 Change the for-loop over InputFilenames to detect ar archives and link them
  in as libraries without searching.
 Change the for-loop over Libraries to explicitly turn on the "search" flag
  to LinkLibrary() that makes LoadLibrary() search for the correct library
  (i.e., when processing -lNAME options.)

llvm-svn: 6316