Integrate change #9030 from maintperl into mainline.

Integrate change #9030 from maintperl into mainline.

Subject: [PATCH 5.6.1] OS/2 cleanup

p4raw-link: @9030 on //depot/maint-5.6/perl: 2105755b4e61318e9489b9a118af8e270a8bc735

p4raw-id: //depot/perl@9031
p4raw-branched: from //depot/maint-5.6/perl@9029 'branch in'
	os2/os2add.sym
p4raw-integrated: from //depot/maint-5.6/perl@9029 'copy in'
	os2/Changes os2/OS2/REXX/REXX.pm os2/OS2/REXX/t/rx_cmprt.t
	os2/os2.sym (@5902..) os2/Makefile.SHs (@8153..)
	os2/OS2/REXX/REXX.xs os2/os2ish.h (@8606..) 'merge in'
	lib/ExtUtils/MM_OS2.pm os2/OS2/REXX/Makefile.PL (@5902..)
	MANIFEST (@8986..) makedef.pl (@8987..) os2/os2.c (@9016..)
	lib/ExtUtils/MM_Unix.pm (@9028..)