Features:
- a second axis can now be displayed in rrd_graph. look for
documentation on second-axis. feature was sponsored by VoltWerk.
Bugfixes:
- rrd_fetch: is more careful when seeking. it should not try to seek
outside the file anymore.
- rrd_graph: CDEF:x= raises an error now and does not segfault
- rrd_graph: --font TITLE:12: problem fixed (affecting cacti)
- rrd_graph: make VDEF work with SHIFT (bug #177)
- rrd_xport: make it work when exporting datasources without
uniform step size.
- rrd_tool: rely on function return values and not on errno. (bug #176)
