Fix known typos

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

llvm-svn: 200018
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index fe87519..377d0d8 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -249,7 +249,7 @@
   ShadowMapping Mapping;
 
   // OR-ing shadow offset if more efficient (at least on x86),
-  // but on ppc64 we have to use add since the shadow offset is not neccesary
+  // but on ppc64 we have to use add since the shadow offset is not necessary
   // 1/8-th of the address space.
   Mapping.OrShadowOffset = !IsPPC64 && !ClShort64BitOffset;