Fix InCallUI crash when post char dialog is shown

When user makes MO video call with post char, such as ";", post char
dialog is shown when call is established.

At this time if user rotate InCallUI screen, InCallUI will crash
because PostCharDialogFragment has no zero argument constructor.

Add zero argument constructor for PostCharDialogFragment, and save the
needed parameter to Bundle.

Change-Id: I3587ad2bc47d4397b78b32d1ec27b8c914e9fb2f