add missing index entries for set/show print sevenbit-strings.
Show which format _GDBN__ will use to print structures.
@item set print sevenbit-strings on
+@kindex set print sevenbit-strings
Print using only seven-bit characters; if this option is set,
_GDBN__ will display any eight-bit characters (in strings or character
values) using the notation @code{\}@var{nnn}. For example, @kbd{M-a} is
is the default.
@item show print sevenbit-strings
+@kindex show print sevenbit-strings
Show whether or not _GDBN__ will print only seven-bit characters.
@item set print union on