bc(1): Sync with openBSD

bc(1): Sync with openBSD

This include the following changes :

 * repair function when used with different scales

 * Better error message on unexpected newline

 * save/restore tty state on SIGTSTP/SIGCONT

 * protect errno from damage in the signal handler

 * make ^D behave well
   dont't echo it and make it work if the cursor is at start of line after a ^C

 * avoid usage of YY_FLUSH_BUFFER

    - avoid YY_FLUSH_BUFFER: it is not signal safe and it does not work as intended
    after the introduction of editline
    - honour editline edit off mode

OpenBSD updated files revisions :
    - scan.l : 1.28
    - bc.y : 1.42
    - bc.library : 1.4
    - extern.h : 1.10
    - tty.c : 1.1

Obtained-from: OpenBSD