[Image-SIG] Convert Function and Palette Mode

[Takekun Sato]

It seems that 'im.convert("P")' always converts
an image with 'Web-Color'.

So, resultant image is surely made up of 216 colors 
such as #333333,#336699,#3366CC,...

How can I change the behavior to make the 'convert()'
to use appropriate color palette other than 'Web-Color'?