PR466:

* Make the linker find lib*.bca files now instead of lib*.bc since those
  are what the makefiles now generate for bytecode archives.
* Make sure the linker only links archives when LinkLibraries is called.
  Previously if it found a lib*.bc file and that file was a bytecode file,
  it would link in the entire bytecode. This could make -lc -lc fail with
  duplicate symbols error but it shouldn't as searching multiple libraries,
  even the same one more than once, is permitted.
* Now that the above problems are corrected, implement the dependent libs
  feature. After the module is linked with all specified libraries, the
  LinkLibraries function will obtain the set of dependent libraries from
  the linked modules and attemp to find and link against those libraries.

llvm-svn: 18428