Revert "configure: Remove test for strlcat"

This reverts commit e4e469a0ed.

It looks like we get to choose between breaking the clang build or the
gcc build. With gcc, we need to ensure that enter xorg/os.h with the
right set of HAVE_STRNDUP et al guards, e.g.

In file included from /usr/include/string.h:630:0,
                 from /usr/include/xorg/os.h:53,
                 from /usr/include/xorg/misc.h:116,
                 from fd.c:34:
/usr/include/xorg/os.h:590:1: error: expected identifier or '(' before '__extension__'
 strndup(const char *str, size_t n);

Reported-by: Arkadiusz Miskiewicz <arekm@maven.pl>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

configure.ac

@@ -62,6 +62,9 @@ AC_DISABLE_STATIC
 AC_PROG_LIBTOOL
 AC_SYS_LARGEFILE
 
+# Check for common libc routines redefined by os.h
+AC_CHECK_FUNCS([strlcpy strlcat strndup], [], [])
+
 # Platform specific settings
 case $host_os in
   *linux*)