Enable preprocess edoc flag

Author: prefiks

rebar.config

@@ -27,6 +27,8 @@
             {platform_define, "^(R|1|2[0123]|24\.[012])", 'USE_ADDRPORTCONNECT'},
             {i, "include"}]}.
 
+{edoc_opts, [{preprocess, true}]}.
+
 {port_env, [{"ERL_LDFLAGS", " -L$ERL_EI_LIBDIR -lei"},
             {"CFLAGS", "$CFLAGS"}, {"LDFLAGS", "$LDFLAGS"}]}.