lib: ignorepattern: Corrected change of isGlob to False in 'slash' state

The 'slash' state in the ignore pattern parsing state machine already
set the isGlob flag to False in its constructor, which incorrectly
treated pattern like 'bin/' not as file glob although they are folder
only file glob. Now the state sets the isGlob flag to false if another
character is found after the '/' character.
lib: ignorepattern: Changed documentation for 'slash-begin' state

The documentation of the 'slash-begin' mentioned that this state starts
a base only file glob which is not completely correct. The pattern which
is described with this pattern could also be a normal one, just with a
'/' character at the beginning.