re-add function prototypes
This commit reverts a part of 0e8219f591f3f17cb7ee361e8a60dbef08145883 which broke icc. See also https://rubyci.org/logs/rubyci.s3.amazonaws.com/icc-x64/ruby-master/log/20191120T010006Z.fail.html.gz
re-add function prototypes
This commit reverts a part of 0e8219f591f3f17cb7ee361e8a60dbef08145883
which broke icc. See also https://rubyci.org/logs/rubyci.s3.amazonaws.com/icc-x64/ruby-master/log/20191120T010006Z.fail.html.gz