Pull up following revision(s) (requested by kre in ticket #914):

usr.bin/printf/printf.c: revision 1.38,1.39

From leot@ on tech-userlevel:
Avoid running off into oblivion when a format string,
or arg to a %b conversion ends in an unescaped backslash.

Patch from Leo slightly modified by me.

Avoid printing error messages twice when an invalid
escape sequence (\ sequence) is present in an arg to a %b
conversion.

(martin)