* modules/xstrtoll: New file.
* MODULES.html.sh (Numeric conversion functions): Add xstrtoll.
* lib/xstrtol.h [HAVE_LONG_LONG_INT]: Declare xstrtoll and xstrtoull.
* lib/xstrtoll.c, lib/xstrtoull.c: New files.
./configure fails if you use this module and lack "long long".
* modules/xstrtoll-tests: New module.
* tests/test-xstrtoll.c, tests/test-xstrtoull.c: New files.
* tests/test-xstrtoll.sh: Like test-xstrtol.c, but use the
new init.sh-based test framework.
