Log Message:
Update to 3.1.7:

Changes from 3.1.6 to 3.1.7
---------------------------
1. Gawk now has support for z/OS (IBM S/390 architecture).

2. Gawk now handles multibyte strings better in [s]printf with field
   widths and such.

3. Gawk now uses libsigsegv to print a message before core dumping. This
   handles infinite recursion of an awk function a little better.
   Use of the library can be disabled at configure time with the
   --disable-libsigsegv option for unusual systems.

4. The handling of BINMODE is now somewhat more sane.

5. A getline from a directory is no longer fatal; instead it returns -1.

6. Per POSIX, special variable names (like FS) cannot be used as function
   parameter names.

7. The new -O / --optimize option enables simple constant folding on
   the parse tree during parsing.  We hope that with time the number
   of optimizations will increase.

8. Updated to the latest autotools: Autoconf 2.63, Automake 1.11,
   Libtool 2.2.6a, and Gettext 0.17. Also latest Bison: 2.4.1.

9. Some improvement in testing for isinf / isnan in builtin.c.

10. Improved the handling of `a = a b c' to be more general.

11. Locale handling for %'d should now work on certain non-Unix /
    non-Linux systems.

12. Lots of bugs fixed, see the ChangeLog for the details.