[PATCH] Rename lld:*_error::_ -> lld:*_error::ErrorCode.

[Michael Spencer]

  The use of _ is a hack to emulate scoped enums. The _ should never be referenced directly. However, since we have scoped enums now, we should just use them.

http://llvm-reviews.chandlerc.com/D1851

COMMIT
  http://llvm-reviews.chandlerc.com/rL192138