configure: fix the check for X11/Xutil.h

At least some solaris enforce the need to #include X11/Xlib.h first.

Thanks to Siegmar Gross for reporting the issue.

(cherry picked from commit 005a7e89b67010952f9d86e905a17b38d18dab7f)
tests/xml: break set and export envvar lines to work

Thanks to Siegmar Gross for reporting the failure.

(cherry picked from commit 635e7ea3653cacee54dce6970dfa1817660cfae9)