Add test case to syntax_tools

The added test case tests a bug when reverting maps in syntax tools.
Fix reverting map in syntax_tools

There was a copy-paste bug in erl_syntax when running
e.g. erl_syntax:revert_forms, affecting maps. Instead of getting
Key/Value you got Key/Key in the resulting abstract form.
ssl: Only allow one next protocol handsake message
ssl: Fix dialyzer spec
Merge branch 'rolkar/fix-syntax_tools-revert-bug/OTP-11930' into maint

* rolkar/fix-syntax_tools-revert-bug/OTP-11930:
  Fix reverting map in syntax_tools
  Add test case to syntax_tools
Merge branch 'ia/ssl/dubble-next-proto/OTP-11926' into maint

* ia/ssl/dubble-next-proto/OTP-11926:
  ssl: Fix dialyzer spec
  ssl: Only allow one next protocol handsake message