Misc typos fixes in ./lib folder

Summary: Found via `codespell -q 3 -I ../clang-whitelist.txt -L uint,importd,crasher,gonna,cant,ue,ons,orign,ned`

Reviewers: teemperor

Reviewed By: teemperor

Subscribers: teemperor, jholewinski, jvesely, nhaehnle, whisperity, jfb, cfe-commits

Differential Revision: https://reviews.llvm.org/D55475

llvm-svn: 348755
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index aa411c0..413956e 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -4354,7 +4354,7 @@
 }
 
 std::string Driver::GetFilePath(StringRef Name, const ToolChain &TC) const {
-  // Seach for Name in a list of paths.
+  // Search for Name in a list of paths.
   auto SearchPaths = [&](const llvm::SmallVectorImpl<std::string> &P)
       -> llvm::Optional<std::string> {
     // Respect a limited subset of the '-Bprefix' functionality in GCC by