Fix known typos

Sweep the codebase for common typos. Includes some changes to visible function
names that were misspelt.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200018 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/APFloat.cpp

@@ -3776,7 +3776,7 @@ APFloat::opStatus APFloat::next(bool nextDown) {
     //                     change the payload.
     if (isSignaling()) {
       result = opInvalidOp;
-      // For consistency, propogate the sign of the sNaN to the qNaN.
+      // For consistency, propagate the sign of the sNaN to the qNaN.
       makeNaN(false, isNegative(), 0);
     }
     break;