getInfo mishandles 'Private' info type

[iustin]

This is how getInfo behaves for Private:

getInfo h i = do
 case i of
    …
  Private -> getInfoStr h (show i) 21

However, the private pointer is a void* pointer, even though the C library handles it as a char* pointer. From the docs:

Please note that for internal reasons, the value is returned as a char pointer, although effectively being a 'void *'. (Added in 7.10.3)

This is also visible in the fact that for set_opt, CurlPrivate takes a Ptr () argument.

Adding a proper return type of Ptr () should be easy, with the note that life of the pointer will then have to be handled manually by the user of the library.

[glguy]

It looks like you're right. If you want to submit a pull request to fix this I can merge it in.