add tuple_calls compiler flag for erlang 21
From http://www.erlang.org/news/123 :
* "Tuple calls" have been removed from the run-time system.
http://erlang.org/download/otp_src_21.0.readme
* OTP-14497
For legacy code that need to use parameterized modules
or tuple calls for some other reason, there is a new
compiler option called tuple_calls. When this option is
given, the compiler will generate extra code that
emulates the old behavior for calls where the module is
a variable.diff --git a/rebar.config b/rebar.config
index adc1d78..014ff05 100644
--- a/rebar.config
+++ b/rebar.config
@@ -1,5 +1,6 @@
% -*- mode: erlang -*-
{erl_opts, [debug_info,
+ tuple_calls,
{platform_define, "^R15", 'gen_tcp_r15b_workaround'},
{platform_define, "^(R14|R15|R16B-)", 'crypto_compatibility'},
{platform_define, "^(R14|R15|R16B|17)", 'rand_mod_unavailable'},
