Add note about known issue with -Wrace_conditions

As noted on the erlang-bugs mailing list:
http://erlang.org/pipermail/erlang-bugs/2014-July/004518.html
ssl: Servers may include an empty SNI-extension
Merge branch 'ia/ssl/empty-sni-from-server/OTP-12198' into maint

* ia/ssl/empty-sni-from-server/OTP-12198:
  ssl: Servers may include an empty SNI-extension
Merge branch 'maint'
Merge branch 'legoscia/patch-8/dialyzer-doc-fix' into maint

* legoscia/patch-8/dialyzer-doc-fix:
  Add note about known issue with -Wrace_conditions
Merge branch 'maint'