nocaseglob and RE matching

[Grisha Levit]

Currently nocaseglob and nocasematch both control case insensitivity
of RE matching (in lib/sh/smatch.c):

  if (glob_ignore_case || match_ignore_case)
    rflags |= REG_ICASE;

However, the documentation suggests that only nocasematch should have
this effect.  I'm guessing this behavior was in bash-3.1 for
compatibility with bash-3.0 (in which nocaseglob *was* the documented
way to turn on case insensitive RE matching, prior to nocasematch
being added) but it doesn't seem to make much sense now.