KWIML: Teach ABI about 'long long' on older GNU

Old GNU compilers do not define __SIZEOF_LONG_LONG__ or
__LONG_LONG_MAX__ but do provide a 64-bit 'long long' type.

Suggested-by: Rolf Eike Beer <eike@sf-mail.de>
Merge branch 'upstream-kwiml' into update-KWIML
Merge topic 'update-KWIML' into next

32fb667 Merge branch 'upstream-kwiml' into update-KWIML
9fdfe07 KWIML: Teach ABI about 'long long' on older GNU