add bindings for instruction description methods to MCInstrDesc

use these new bindings instead of MCInstrAnalysis bindings in
llvm.mc.Instr because MCInstrAnalaysis is just a thin layer
encapsulating MCInstrInfo that seems largely pointless.

test/example-disassemble.py

@@ -16,7 +16,8 @@ if llvm.version >= (3, 4):
             'is_indirect_branch',
             'is_call',
             'is_return',
-            'is_terminator'
+            'is_terminator',
+            'is_barrier'
         ]
 
         print("print instructions")