Backport candidates to 2.0 branch

[NIIBE Yutaka]

Hello,

I updated po/ja.po in STABLE-BRANCH-2-0.  Then, I examined the changes
in master after 2.1.2 to today.

Following five commits can be just cherry-picked to STABLE-BRANCH-2-0.

scd: Fix possible NULL deref in apdu.c
author	Werner Koch <wk at gnupg.org>	
	Sun, 15 Mar 2015 11:15:55 +0000 (12:15 +0100)
commit	ef0a3abf7305133d071bf1a94a7f461082f9a9aa

agent: Fix length test in sshcontrol parser.
author	Werner Koch <wk at gnupg.org>	
	Sun, 15 Mar 2015 12:04:48 +0000 (13:04 +0100)
commit	3529dd8bb5bafc4e02915648d5f409bd27a9cc37

gpgparsemail: Fix case of zero length continuation lines.
author	Werner Koch <wk at gnupg.org>	
	Thu, 9 Apr 2015 17:06:33 +0000 (19:06 +0200)
commit	3fbeba64a8bfb2b673230c124a3d616b6568fd2f

gpgparsemail: Fix last commit (3f2bdac)
author	Werner Koch <wk at gnupg.org>	
	Fri, 10 Apr 2015 06:34:35 +0000 (08:34 +0200)
commit	9433661419043431a6cfc7d84c8450e0b2f6c353

scd: better handling of extended APDU. master
author	NIIBE Yutaka <gniibe at fsij.org>	
	Tue, 14 Apr 2015 05:17:03 +0000 (14:17 +0900)
commit	971d558e862db878a7310e06ed7116dbe36886ab
--