Fix function relocations in libzpool

binutils 2.23.1 fails in situations that generate function relocations
on PowerPC and possibly other architectures. This causes linking of
libzpool to fail because it depends on libnvpair. We add a dependency on
libnvpair to lib/libzpool/Makefile.am to correct that.

Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1267
Remove unused machelf.h header

The machelf.h header is never included by anything in the zfs
build process.  It is all effectively dead code which can be
safely removed.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1265