ticket:10557: Fix some zOS build errors caused by missing exports and pthread macros

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@34733 251d0590-4201-4cf1-90de-194747b24ca1
ticket:10549: Fixed some problems in test case description in collperf2.

git-svn-id: http://source.icu-project.org/repos/icu/icu/trunk/source@34734 251d0590-4201-4cf1-90de-194747b24ca1