Improve build compatibility across platforms
The patches attached to this issue are based on the patches available in the pkgsrc system ( https://github.com/NetBSD/pkgsrc/tree/pkgsrc-2019Q1/security/lasso/patches ). They improve the ability to build lasso on different platforms.
In the configure script, "test(1)" is called with a "==". From the test manpage(https://linux.die.net/man/1/test), the standard string comparison operator in test is "=" and not "==", and although "==" works with the most commonly used systems, "=" gives better compatibility.
On lasso/xml/tools.c, _XOPEN_SOURCE is defined. This fails on sun.