libxpm: upgrade 3.5.15 -> 3.5.16

libxpm: upgrade 3.5.15 -> 3.5.16

Changelog:
===========
test: skip compressed file tests when --disable-open-zfile is used
itlab CI: build with each of --enable-open-zfile & --disable-open-zfile
configure: correct error message to suggest --disable-open-zfile
Fix a memleak in ParsePixels error code path
Fix CVE-2022-44617: Runaway loop with width of 0 and enormous height
open-zfile: Make compress & uncompress commands optional
Require LT_INIT from libtool 2 instead of deprecated AC_PROG_LIBTOOL
test: Use PACKAGE_BUGREPORT instead of hard-coded URL's
test: Add simple test cases for functions in src/rgb.c
xpmReadRgbNames: constify filename argument
XpmCreateDataFromXpmImage: Fix misleading indentation
parse.c: Wrap FREE_CIDX definition in do { ... } while(0)
parse.c: remove unused function xstrlcpy()

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>