Prefer other types to int in misc.c

Prefer other types to int in misc.c

* src/misc.c (quote_copy_string, tar_savedir):
Use bool for booleans.  All uses changed.
(quote_copy_string): Use char for chars.
(unquote_string): Return void, since nobody uses return value.
(unquote_string): Check for overflow in escapes like \777.
(wdcache): Now array of idx_t not int, since in theory it
might contain values greater than INT_MAX.  All uses changed.