warning: implicit declaration of function 'readahead'

["Mathieu Malaterre" <mathieu.malaterre@gmail.com>]

Hello,

  I am getting this annoying warning:

warning: implicit declaration of function 'readahead'

  Looking at the man page of readahead I need to include fcntl.h to
get the declaration. But after digging in the source the readahead is
only accessible if __USE_GNU is defined, which in turn is only defined
if _GNU_SOURCE is defined.

  So either the declaration needs to be moved out of the __USE_GNU, or
the documentation needs to be updated to specify the requirement for
_GNU_SOURCE before the #include, correct ?

Thanks,
-- 
Mathieu