regcomp.c: Comment fixes
t/uni/variables.t: Fix typo

This caused failures only in EBCDIC.  The variable $chr is what was
intended, but due to a missing '$', we got the variable $_ which differs
from $chr only on EBCDIC.
Makefile.SH: Fix so works in EBCDIC
t/re/regexp.t: Properly handle \c?[ in regex_sets

t/re/regex_sets.t is actually handled by regexp.t, skipping all tests
that don't have a [bracketed character class].  Prior to this commit,
\[ and \c[ were thought to be such a class, when in fact they aren't.
regen/ebcdic.pl: Allow making tables in hex

This allows the source to be easily edited to create ebcdic translations
tables in hex which is easier to debug, but won't fit in an 80 column
window.  I suppose it could be controlled by an environment variable,
but for now, it's just going to be hard-set to 1 or 0.
op/index.t: Fix tests for EBCDIC

Commit 8a38a836 erroneously translates literals into the native
encoding, causing a double translation, which is garbage.