help: interpret boolean string values for help.autocorrect

help: interpret boolean string values for help.autocorrect

A help.autocorrect value of 1 is currently interpreted as "wait 1
decisecond", which can be confusing to users who believe they are setting a
boolean value to turn the autocorrect feature on.

Interpret the value of help.autocorrect as either one of the accepted list
of special values ("never", "immediate", ...), a boolean or an integer. If
the value is 1, it is no longer interpreted as a decisecond value of 0.1s
but as a true boolean, the equivalent of "immediate". If the value is 2 or
more, continue treating it as a decisecond wait time.

False boolean string values ("off", "false", "no") are now equivalent to
"never", meaning that guessed values are still shown but nothing is
executed. True boolean string values are interpreted as "immediate".

Signed-off-by: Scott Chacon <schacon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>