Fix FastDateParser#getStrategy(char, int, Calendar) javadoc (closes #242)

The javadoc refers to a formatField parameter, which the method doesn't
have.
Reading the description and the method's code, this documentation
clearly refers to the f parameter.

This patch fixes the javadoc and aligns it with the method's parameters.

src/main/java/org/apache/commons/lang3/time/FastDateParser.java

@@ -548,7 +548,7 @@ public class FastDateParser implements DateParser, Serializable {
 
     /**
      * Obtain a Strategy given a field from a SimpleDateFormat pattern
-     * @param formatField A sub-sequence of the SimpleDateFormat pattern
+     * @param f A sub-sequence of the SimpleDateFormat pattern
      * @param definingCalendar The calendar to obtain the short and long values
      * @return The Strategy that will handle parsing for the field
      */