[PATCH] Introduce new gold plugin option "relocation-pic"

[Alexey Volkov]

  Unfortunately my last patch cannot work with -Wl compiler option.
  E.g. passing -Wl,-shared will not set OPT_shared variable and so -shared and -pie both passed to linker.
  Linker will complain about incompatible options.
  I am not sure if parsing -Wl option value for shared, static, etc is acceptable here.
  In my first patch addition of new gold plugin option does not have such problems.

http://llvm-reviews.chandlerc.com/D2668