Attributes: add a new allocptr attribute

This continues the push away from hard-coded knowledge about functions
towards attributes. We'll use this to annotate free(), realloc() and
cousins and obviate the hard-coded list of free functions.

Differential Revision: https://reviews.llvm.org/D123083

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -647,6 +647,8 @@ static uint64_t getAttrKindEncoding(Attribute::AttrKind Kind) {
     return bitc::ATTR_KIND_JUMP_TABLE;
   case Attribute::MinSize:
     return bitc::ATTR_KIND_MIN_SIZE;
+  case Attribute::AllocatedPointer:
+    return bitc::ATTR_KIND_ALLOCATED_POINTER;
   case Attribute::Naked:
     return bitc::ATTR_KIND_NAKED;
   case Attribute::Nest: