GNU tar v1.13.25 fails to compile on AIX 5.1

[Petter Reinholdtsen]

I fetched <URL:ftp://alpha.gnu.org/gnu/tar/tar-1.13.25.tar.gz>, and
tried to compile it on AIX 5.1.  It fail with the following error
message:

  cc-wrapper -DHAVE_CONFIG_H -I. -I. -I.. -I../intl -g -c `test -f
    xstrtoimax.c || echo './'`xstrtoimax.c
  "xstrtol.c", line 90.10: 1506-343 (S) Redeclaration of strtoimax
    differs from previous declaration on line 673 of
    "/usr/include/inttypes.h".
  "xstrtol.c", line 90.10: 1506-050 (I) Return type "long long" in
    redeclaration is not compatible with the previous return type
    "long".
  make[1]: Leaving directory
    `/usit/hufflepuff/local/store/hufflepuff/gtar-c/src-1.13.25-rs6aix5/lib'
  make[1]: *** [xstrtoimax.o] Error 1

(cc-wrapper is a script to set the needed options to the C compiler.)

The problem is that the prototype of strtoimax() returns 'long' unless
__64BIT__ is defined.  I was able to compile v1.13, so this is a new
problem.

I looked at the source, but have no idea how to fix the problem
without restructuring a lot of code.

Any suggestions?