configure: test for -Wundef
configure: test for -Wundef

Change-Id: Ia4bcde5276ae9572c5b3152e578d59a4e3552988

PKRoma/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp