Integrate two DJGPP portability patches from the 5.6.2 branch :

Integrate two DJGPP portability patches from the 5.6.2 branch :

[20859]
Two portability patches for DJGPP from Richard Dawe
<rich@phekda.freeserve.co.uk>.
Message-Id: <E19qfNh-0000Zq-00@phekda.freeserve.co.uk>

[20911]
Don't uppercase automatically all environment variables on DJGPP.
(reported by Richard Dawe, this breaks portability of Unix
scripts.) Don't change the behaviour on plain MS/DOS.
p4raw-link: @20911 on //depot/maint-5.6/perl-5.6.2: 91a64263ab3d9ea51fa198428b79b128d13386a5
p4raw-link: @20859 on //depot/maint-5.6/perl-5.6.2: e61553d05d06f2b080893dabff3b9134ba8b77f7

p4raw-id: //depot/perl@20913
p4raw-edited: from //depot/maint-5.6/perl-5.6.2@20912 'edit in' perl.c
	(@20322..)
p4raw-integrated: from //depot/maint-5.6/perl-5.6.2@20912 'merge in'
	djgpp/djgppsed.sh dosish.h (@20322..)