Bail early and avoid warnings on 32 bit Perl builds

[demerphq]

In 03d0996 the U64 class was removed
and zipdetails was made 64 bit only. This causes warnings and test
failures (t/porting/utils.t) on i386 builds of perl core when
IO-Compress 2.105 was merged.
Perl/perl5#19618
# Failed test 83 - utils/zipdetails compiles at porting/utils.t line 85
# got "Integer overflow in hexadecimal number at utils/zipdetails line 1432.
Integer overflow in hexadecimal number at utils/zipdetails line 2247.
Integer overflow in hexadecimal number at utils/zipdetails line 2248.
Integer overflow in hexadecimal number at utils/zipdetails line 2249.
Integer overflow in hexadecimal number at utils/zipdetails line 2250.
Integer overflow in hexadecimal number at utils/zipdetails line 2251.
Integer overflow in hexadecimal number at utils/zipdetails line 2252.
Integer overflow in hexadecimal number at utils/zipdetails line 2253.
Integer overflow in hexadecimal number at utils/zipdetails line 2254.
utils/zipdetails syntax OK
"
# expected "utils/zipdetails syntax OK
"
t/porting/utils .................................................. FAILED at test 83

The code also makes use of unpack "Q" so it wouldn't work on 32 bit
builds anyway.

This patch adds a check very early in the script to see if the perl supports
pack "Q", and it does not, indicating it is a 32 bit perl, then it bails out.
If the script is run under -c it bails out without a message, and otherwise
it prints out a message, and exits with error code 1.

$ ./perl -Ilib utils/zipdetails
zipdetails requires 64 bit integers, this Perl has 32 bit integers.

This alone does not make it pass t/porting/utils.t in Perl core, we need
a corresponding patch to t/porting/utils.t which I will also push.

See Perl/perl5#19618 for the corresponding patch.

[pmqs]

Thanks @demerphq

merging for now to fix the immediate issue.