Merge reproc changes from dev.

src/api/api.c

@@ -4,12 +4,14 @@
 int luaopen_system(lua_State *L);
 int luaopen_renderer(lua_State *L);
 int luaopen_regex(lua_State *L);
+int luaopen_process(lua_State *L);
 
 
 static const luaL_Reg libs[] = {
   { "system",    luaopen_system     },
   { "renderer",  luaopen_renderer   },
   { "regex",     luaopen_regex   },
+  { "process",   luaopen_process    },
   { NULL, NULL }
 };