Standardise on pc

When riak is built, bitcask determines which version of pc is used.  All other deps are tested with openriak-3.4 pc, so bitcask should use this too.

Author: martinsumner

rebar.config

@@ -63,7 +63,12 @@
    ]}
  ]}.
 
-{plugins, [pc, {eqc_rebar, {git, "https://github.com/Quviq/eqc-rebar", {branch, "master"}}}]}.
+{plugins,
+  [
+    {pc, {git, "https://github.com/OpenRiak/port_compiler", {branch, "openriak-3.4"}}},
+    {eqc_rebar, {git, "https://github.com/Quviq/eqc-rebar", {branch, "master"}}}
+  ]
+}.
 
 {provider_hooks,
  [