Install sk man page to the right directory.

https://bugs.gentoo.org/show_bug.cgi?id=481276

--- inkscape-0.91pre3/Makefile.am
+++ inkscape-0.91pre3/Makefile.am
@@ -561,7 +561,7 @@
 manja_DATA = inkscape.ja.1
 manjadir = $(mandir)/ja/man1
 
-mansk_DATA = inkscape.ja.1
+mansk_DATA = inkscape.sk.1
 manskdir = $(mandir)/sk/man1
 
 manzhtw_DATA = inkscape.zh_TW.1