Support writing to async proc STDIN also.

Includes an NQP_REVISION bump to get MoarVM improvements that enable
this.

src/core/Proc/Async.pm

@@ -21,6 +21,7 @@ my class X::Proc::Async::AlreadyStarted is Exception {
 my class Proc::Async {
     has $.path;
     has @.args;
+    has $.w;
     has Bool $!started;
     has $!stdout_supply;
     has Bool $!stdout_supply_chars;
@@ -129,6 +130,7 @@ my class Proc::Async {
                 });
         }
         nqp::bindkey($callbacks, 'buf_type', buf8.new);
+        nqp::bindkey($callbacks, 'write', True) if $.w;
 
         $!process_handle := nqp::spawnprocasync($scheduler.queue,
             $args-without, $*CWD.Str, $hash-without, $callbacks);
@@ -190,6 +192,11 @@ my class Proc::Async {
         $p
     }
 
+    method close_stdin() {
+        nqp::closefh($!process_handle);
+        True;
+    }
+
     method kill($signal = 1) {
         nqp::killprocasync($!process_handle, $signal.Int)
     }

tools/build/NQP_REVISION

@@ -1 +1 @@
-2014.07-82-gc2362f4
+2014.07-83-gdaaf098