Specifies whether date/time parsing is to be lenient. With
lenient parsing, the parser may use heuristics to interpret inputs that
do not precisely match this object's format. Without lenient parsing,
inputs must match this object's format more closely.
Note: ICU 53 introduced finer grained control of leniency (and added
new control points) making the preferred method a combination of
setCalendarLenient() & setBooleanAttribute() calls.
This method supports prior functionality but may not support all
future leniency control & behavior of DateFormat. For control of pre 53 leniency,
Calendar and DateFormat whitespace & numeric tolerance, this method is safe to
use. However, mixing leniency control via this method and modification of the
newer attributes via setBooleanAttribute() may produce undesirable