Remove the 'asciir' re subpragma. Should instead implement

Remove the 'asciir' re subpragma.  Should instead implement
the 'physical vs logical' range scheme:

\xAA-\xCC is a native physical range, you want that range of
codepoints in your native encoding.  In EBCDIC the codepoints
in the gaps (between i-j and r-s) should be included.

\x{AA}-\x{CC} is a physical Unicode range, you want that range of
codepoints in Unicode.

a-z is a logical range, you want that range of 'logical' codepoints
in your native encoding.  In EBCDIC the codepoints in the gaps
(between i-j and r-s) should not be included.

Mixed cases (a-\xAA, etc) should either be errors, or maybe
the 'logical' endpoints should be converted to native/Unicode
codepoints, and the range handled as a physical range.

'Logical endpoints' are to be recognized only in the A-Z, a-z,
and 0-9 ranges.  Probably a warning should be given for mixed
cases like A-z or a-9 (since such expressions are encoding
dependent), with a recommendation to use physical ranges.

p4raw-id: //depot/perl@10085