Fix uses of reserved identifiers starting with an underscore followed by an uppercase letter

This covers essentially all of llvm's headers and libs. One or two weird
cases I wasn't sure were worth/appropriate to fix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232394 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Option/ArgList.cpp

@@ -340,9 +340,8 @@ const char *InputArgList::MakeArgString(StringRef Str) const {
 
 //
 
-DerivedArgList::DerivedArgList(const InputArgList &_BaseArgs)
-  : BaseArgs(_BaseArgs) {
-}
+DerivedArgList::DerivedArgList(const InputArgList &BaseArgs)
+    : BaseArgs(BaseArgs) {}
 
 DerivedArgList::~DerivedArgList() {}