Fix typos in clang

Found via codespell -q 3 -I ../clang-whitelist.txt
Where whitelist consists of:

  archtype
  cas
  classs
  checkk
  compres
  definit
  frome
  iff
  inteval
  ith
  lod
  methode
  nd
  optin
  ot
  pres
  statics
  te
  thru

Patch by luzpaz! (This is a subset of D44188 that applies cleanly with a few
files that have dubious fixes reverted.)

Differential revision: https://reviews.llvm.org/D44188

llvm-svn: 329399
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 92fb8f0..1a62192 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -396,7 +396,7 @@
 
   // Handle Apple-specific options available here.
   if (Target.isOSBinFormatMachO()) {
-    // If an explict Darwin arch name is given, that trumps all.
+    // If an explicit Darwin arch name is given, that trumps all.
     if (!DarwinArchName.empty()) {
       tools::darwin::setTripleTypeForMachOArchName(Target, DarwinArchName);
       return Target;