s3/swat: use strlcat instead of strncat to fix build on old Linux distros

SLES 9's glibc for example had weird macros where the use of strncat resulted
in the use of strcat which we don't allow.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User: Björn Jacke <bj@sernet.de>
Autobuild-Date: Thu Aug  4 17:50:24 CEST 2011 on sn-devel-104
(cherry picked from commit d3b4d75364210e2d2a4a1cd806f28b0021f22909)

Fix bug #8362 (build issue on old glibc systems).
(cherry picked from commit 87fa72a5202fe3780d4a61289bf755027cd078f4)
(cherry picked from commit 552ccc6588b0744ae9b3731b1406749baea03d5a)
(cherry picked from commit b941edf9c20bd6a92aec2a62be5b830db1194ce8)