[Mips] s/context/ctx/ for consistency and reduce lines lengths.

No functional changes.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@213310 91177308-0d34-0410-b5e6-96231b3b80d8
Use std::function instead of llvm::function_ref.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@213312 91177308-0d34-0410-b5e6-96231b3b80d8
Remove all uses of llvm::function_ref from LLD.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@213313 91177308-0d34-0410-b5e6-96231b3b80d8