Fix a ton of comment typos found by codespell.  Patch by
Luis Felipe Strano Moraes!

llvm-svn: 129558
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index 3a63258..c3169ac 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -3564,7 +3564,7 @@
 }
 
 bool APFloat::getExactInverse(APFloat *inv) const {
-  // We can only guarantee the existance of an exact inverse for IEEE floats.
+  // We can only guarantee the existence of an exact inverse for IEEE floats.
   if (semantics != &IEEEhalf && semantics != &IEEEsingle &&
       semantics != &IEEEdouble && semantics != &IEEEquad)
     return false;