List of bugs fixed.

1. ofs-rebuild: OFS value used to rebuild the record was incorrect.
Fixed August 19, 2014. Revised fix August 2018.

2. system-status: Instead of a floating-point division by 256, use
the wait(2) macros to create a reasonable exit status. Fixed March 12, 2016.

3. space: Use provided xisblank() function instead of ispace() for
matching [[:blank:]].

4. a-format: Add POSIX standard %a and %A to supported formats. Check
at runtime that this format is available.

5. decr-NF: Decrementing NF did not change $0. This is a decades-old
bug. There are interactions with the old and new value of OFS as well.
Most of the fix came from the NetBSD awk.

6. string-conv: String conversions of scalars were sticky.  Once a
conversion to string happened, even with OFMT, that value was used until
a new numeric value was assigned, even if OFMT differed from CONVFMT,
and also if CONVFMT changed.

7. unary-plus: Unary plus on a string constant returned the string.
Instead, it should convert the value to numeric and give that value.

8. concat-assign-same: Concatenation previously evaluated both sides of the
expression before doing its work, which, since assign() evaluates to the cell
being assigned to, meant that expressions like "print (a = 1) (a = 2)" would
print "22" rather than "12".

9. missing-precision: When using the format string "%*s", the precision
argument was used without checking if it was present first.

10. missing-precision: When using the format string "%*s", the precision
argument was used without checking if it was present first.

11. fmt-overflow: The buffer used for OFMT/CONVFMT conversions was written
to with sprintf(), which meant that some conversions could write past the
end.

12. numeric-subsep, numeric-fs, numeric-output-seps, numerics-rs: If SUBSEP,
FS, RS, OFS, or ORS were set to a numeric value, then their string values
wouldn't always be generated before being needed.

13. subsep-overflow: The length of SUBSEP needs to be rechecked after
calling execute(), in case SUBSEP itself has been changed.