Need detail: backslash-newline sequences inside of single-quoted strings

[gk]

I have searched info make on GNU make manual section "Command Execution" 
but found no mention of the details mentioned below, concerning backslash 
inside of single-quoted strings.

Can you provide any detail?

NOTES file says:
>* WARNING: Backward-incompatibility!
  In order to comply with POSIX, the way in which GNU make processes
  backslash-newline sequences in command strings has changed.  If your
  makefiles use backslash-newline sequences inside of single-quoted
  strings in command scripts you will be impacted by this change.  See
  the GNU make manual section "Command Execution" (node "Execution") for
  details.