Use -lbsd for strlcat/strlcpy, if needed and available

On BSD systems, strlcat and strlcpy are included in the C library and
nothing special is needed. On Linux systems they are not, but libbsd may
be available to provide them. Use it if so.

This also adds wstrlcat and wstrlcpy instead of trying to maybe-provide
strlcat and strlcpy themselves, as that way there is no risk of symbol
conflicts. Not bumping the library version at this time, that should be
done (if necessary) before release.

Signed-off-by: Brad Jorsch <anomie@users.sourceforge.net>

configure.ac

@@ -168,11 +168,31 @@ AC_CHECK_FUNCS(gethostname select poll strcasecmp strncasecmp \
 
 dnl Check for strlcat/strlcpy
 dnl =========================
-dnl XXX: A clean way to use libbsd-supplied equivalents should be come up
-dnl      with. This is a tricky-ish problem, as it will require a conditional
-dnl      inclusion of an extra header everywhere there is string.h included.
-AC_CHECK_FUNC(strlcat, AC_DEFINE(HAVE_STRLCAT, 1, Check for strlcat))
-AC_CHECK_FUNC(strlcpy, AC_DEFINE(HAVE_STRLCPY, 1, Check for strlcpy))
+AC_ARG_WITH([libbsd],
+  [AS_HELP_STRING([--without-libbsd], [do not use libbsd for strlcat and strlcpy [default=check]])],
+  [AS_IF([test "x$with_libbsd" != "xno"],
+    [with_libbsd=bsd]
+    [with_libbsd=]
+  )],
+  [with_libbsd=bsd])
+
+tmp_libs=$LIBS
+AC_SEARCH_LIBS([strlcat],[$with_libbsd],
+  [AC_DEFINE(HAVE_STRLCAT, 1, [Define if strlcat is available])],
+  []
+)
+AC_SEARCH_LIBS([strlcpy],[$with_libbsd],
+  [AC_DEFINE(HAVE_STRLCAT, 1, [Define if strlcpy is available])],
+  []
+)
+LIBS=$tmp_libs
+
+LIBBSD=
+AS_IF([test "x$ac_cv_search_strlcat" = "x-lbsd" -o "x$ac_cv_search_strlcpy" = "x-lbsd"],
+  [LIBBSD=-lbsd
+   AC_CHECK_HEADERS([bsd/string.h])]
+)
+AC_SUBST(LIBBSD)
 
 dnl Check for inotify
 dnl =================