Pod::Escapes::Escapes.pm: Fix typo in comment
Pod::Escapes::Escapes.pm: Reorder structure defns

This just moves some initialization code en-masse to earlier in the
file, with no other changes.  This is in preparation for a future commit
where other initialization code will now be able to use the moved stuff.
Pod::Escapes::Escapes.pm: Fill %Name2character better for EBCDIC

This commit does several things for filling in %Name2character.

1) Several special values were repeated in the file, like "&lt" meaning
"<".  Now there is only one occurrence each.

2) On Perls that have utf8::unicode_to_native (>= v5.7.3) that function
is used to get complete EBCDIC coverage, instead of the previous just a
few things.

3) On these later Perls, there is now only one code path that is used
for both ASCII and EBCDIC.  This decreases EBCDIC maintenance cost.

4) On earlier Perls, there is better EBCDIC coverage, from using
%Latin1Code_to_fallback.

The extra calls to utf8::unicode_to_native are done only at
initialization, and it is planned to have the compiler optimize these
out in v5.22.
Pod::Escapes::Escapes.pm: Generalize for EBCDIC

Some special handling for EBCDIC is unnecessary.  %Name2character
now already contains the info we need for any platform, so it can be
used where applicable and the previous special handling removed.

But numeric escapes are always Unicode, and need to be translated to
native values before finding their chr.  This commit adds a
function call to do that translation.  This is done even on ASCII
platforms where the function just returns its argument.  I did this
because it generally is better to not have separate code paths for
different platforms.  It is planned to change the Perl compiler to
optimize out this function call on ASCII platforms in Perls starting in
v5.22, so that there will be no performance hit at all for them.  And I
suspect that numeric escapes are relatively infrequently used.  But if
you would rather avoid the performance hit in earlier Perls, the code
could be refactored slightly to accomplish this, with the small extra
maintenance cost of having platform-dependent code branches.
Pod::Escapes: doc clarification