[ADT/Support] Add includes to fix module build

Current Clang complains that 'size_t' / 'reference_wrapper' "must be
declared before it is used."

Author: hahnjo

llvm/include/llvm/ADT/bit.h

@@ -15,6 +15,7 @@
 #define LLVM_ADT_BIT_H
 
 #include "llvm/Support/Compiler.h"
+#include <cstddef> // for std::size_t
 #include <cstdint>
 #include <limits>
 #include <type_traits>

llvm/include/llvm/Support/ErrorOr.h

@@ -16,6 +16,7 @@
 #define LLVM_SUPPORT_ERROROR_H
 
 #include <cassert>
+#include <functional> // for std::reference_wrapper
 #include <system_error>
 #include <type_traits>
 #include <utility>