sys_read_dir() now has a parameter for the maximum number of dirents that
are handled by the upper layer - which is currently 1.
Added a comment in fd.h to ease the location of the sys|user prototypes
of the corresponding functions in fd.c.
git-svn-id: file:///srv/svn/repos/haiku/trunk/current@58 a95241bf-73f2-0310-859d-f6bbb57e9c96
