Rename path libpath in .linker-options.

[ruiu]

Summary

"path" is too generic name for -L or --library-path because a lot of
linker options take paths as arguments. This change renames the option
to avoid confusion.

[compnerd]

Sure, I'm not really tied to the names. Furthermore, I think that we will most likely have to revisit them anyways when the frontend changes are made as a different set of people may also have opinions on the cfe side :-) (which is why I really was trying to push the conversion to the side).

[ruiu]

I want this file to be the de facto standard document about the .linker-options section until we formalize it in a real standard document. That's why I wanted to update this doc.

llvm/trunk/docs/Extensions.rst

 
 LLVM emits the following options:
   - lib
 
     The parameter identifies a library to be linked against.  The library will
     be looked up in the default and any specified library search paths
     (specified to this point).
 
-  - path
+  - libpath
 
     The paramter identifies an additional library search path to be considered
     when looking up libraries after the inclusion of this option.
 
 Target Specific Behaviour
 =========================
 
 X86