Checking Run Time Behavior
==========================
Sometimes you need to find out how a system performs at run time,
such as whether a given function has a certain capability or bug. If
you can, make such checks when your program runs instead of when it is
configured. You can check for things like the machine's endianness when
your program initializes itself.
If you really need to test for a run-time behavior while configuring,
you can write a test program to determine the result, and compile and
run it using `AC_TRY_RUN'. Avoid running test programs if possible,
because using them prevents people from configuring your package for
cross-compiling.