Add a FIXME that assumes we maintain backward compatibility until the next major release.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163195 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Bitcode/Reader/BitcodeReader.cpp

@@ -1246,6 +1246,7 @@ bool BitcodeReader::ParseConstants() {
       break;
     }
     // This maintains backward compatibility, pre-'nsdialect'.
+    // FIXME: Remove with the 4.0 release.
     case bitc::CST_CODE_INLINEASM_OLD: {
       if (Record.size() < 2) return Error("Invalid INLINEASM record");
       std::string AsmStr, ConstrStr;