Workaround for LLVM PR 3861 (http://llvm.org/PR3861).

(LLVM abort()s in codegen if the second integer in a return value is <= i8 on
x86/x86-64)

This was breaking native compilation of Tango's TempFile module on x86-64.

gen/abi-x86-64.cpp

@@ -400,6 +400,15 @@ namespace x86_64_D_cc {
     bool retStructInRegs(TypeStruct* st) {
         // 'fastcc' allows returns in up to two registers of each kind:
         DRegCount state(2, 2, 2);
+    #if 1
+        // TODO: Disable this if and when LLVM PR 3861 gets fixed.
+        
+        // LLVM currently doesn't allow a second int to be an i1 or i8.
+        // (See <http://llvm.org/PR3861>)
+        // Rather than complicating shouldPassStructInRegs(), just disallow
+        // second integers for now.
+        state.ints = 1;
+    #endif
         return shouldPassStructInRegs(st, state);
     }