Update mksh to R43 (formal release, from tarball)

Update mksh to R43 (formal release, from tarball)

The files in src/ are just the unmodified mksh release .tgz
and is Not a Contribution to Android, it’s the upstream code
project. ChangeLog: https://www.mirbsd.org/mksh.htm#clog

Changes, other than upstream mksh code:
• update Copyright years
• sync with moving to a different AOSP project and other AOSP changes
• mkmf.sh: add test compilation mode
• be conservative in filedescriptor usage
• don’t compile the $MirOS$ RCS IDs into the binary to save space
• enable UTF-8 mode, to match reality
• help memory leak debugging by adding -DDEBUG_LEAKS
• update rest of mkmf.sh to work with updated AOSP and mksh
• use ro.product.device property as default hostname in mkshrc
  (originally submitted by John Michelau <john.michelau@motorola.com>)
• do not export PS1 in mkshrc (cross-shell developers agreed on this)
• add “more” function to mkshrc to get a simplistic pager
• add “hd” and “setenv” functions to mkshrc for better UX
• mention Launchpad as upstream bugtracker as comment in mkshrc
• change TMPDIR to /data/local/tmp for now, as /sqlite_stmt_journals is gone
  (although this is still no full replacement, it’s better than before)
• address the segfaults seen by DONG-DONG YANG

Change-Id: I2d4d175bc5163b3d6f5098024f98f316fe812e55