Log Message:
Update libksba to 1.3.4, fixing several vulnerabilities.

Noteworthy changes in version 1.3.4 (2016-05-03) [C19/A11/R4]
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 * Fixed two OOB read access bugs which could be used to force a DoS.

 * Fixed a crash due to faulty curve OID lookup code.

 * Synced the list of supported curves with those of Libgcrypt.

 * New configure option --enable-build-timestamp; a build timestamp is
   not anymore used by default.