Improve global vars for perlcc (DMUEY)

    - simplify scalar-via-blob syntax
    - account for both byte strings and unicode strings
    - add SMALL COMMERCIAL AT to list of possible @ signs

Prompted by https://code.google.com/p/perl-compiler/issues/detail?id=143

All tests pass when run under 5.6.2, 5.8.8, 5.16.0, and 5.18.1
use Unicode::UCD::UnicodeVersion instead of perl version;
don't SKIP strings with \P{Assigned} if conversion is supposed to fail due to invalid characters
use utf8_to_uvuni_buf if available (perl 5.15.9 and higher)
use NATIVE_TO_UNI instead of utf8_to_uvuni_buf (which is deprecated in perl 5.19.4)
update Changes, increase Net::IDN::UTS46 version
Merge branch 'master' of https://github.com/dmuey/Net-IDN-Encode into dmuey-master:
- simplify scalar-via-blob syntax
- add SMALL COMMERCIAL AT to list of possible @ signs

Not Merged:
- account for both byte strings and unicode strings

Cleanup:
- use user-defined character classes \p{IsIDNADot} and \p{IsIDNAAtsign} instead
  of global variables.
- update documentation to include small commerical at

Conflicts:
	lib/Net/IDN/Encode.pm
cleanup: bytes variants don't need utf8 STDOUT/STDERR
update version dependencies, new version 2.099_20131227