editors/le: fix build with recent libc++ headers

As reported on the ports mailing lists, with recent libc++ headers on
e.g. 15.0-CURRENT, 13.4 or 14.2, editors/le fails with errors similar
to:

/usr/include/c++/v1/ios:257:25: error: expected ')'
  257 |   static const fmtflags hex         = 0x0008;
      |                         ^
./edit.h:158:26: note: expanded from macro 'hex'
  158 | #define hex     (editmode==HEXM)
      |                          ^
/usr/include/c++/v1/ios:257:25: note: to match this '('
./edit.h:158:17: note: expanded from macro 'hex'
  158 | #define hex     (editmode==HEXM)
      |                 ^

This is because edit.h defines a hex macro, and this clashes with
std::hex from the libc++ headers.

To fix the build, use post-patch to rename the hex macro to is_hex.

PR: 281141
Reported by: J David <j.david.lists@gmail.com>
Approved by: zi (maintainer)
MFH: 2024Q3