Fix unaligned memory access when reading INPUT_FILE_OFFSETS data

[teemperor]

Summary

The blob data is unaligned, so we also should read it as such. Should fix the random failures with the sanitizer builds.

[v.g.vassilev]

LGTM!

lib/Serialization/ASTReader.cpp

case MODULE_MAP_FILE: {
       break;
     }
     case INPUT_FILE_OFFSETS: {
       if (!NeedsInputFiles)
         break;
 
       unsigned NumInputFiles = Record[0];
       unsigned NumUserFiles = Record[1];
-      const uint64_t *InputFileOffs = (const uint64_t *)Blob.data();
+      const llvm::support::unaligned_uint64_t *InputFileOffs =
+          (const llvm::support::unaligned_uint64_t *)Blob.data();
       for (unsigned I = 0; I != NumInputFiles; ++I) {
         // Go find this input file.
         bool isSystemFile = I >= NumUserFiles;
 
         if (isSystemFile && !NeedsSystemInputFiles)
           break; // the rest are system input files
 
         BitstreamCursor &Cursor = InputFilesCursor;