Fix examples 2

These changes were made while testing stability of pytables-3.1.1-r1 package on x86 system on Gentoo/Linux.

Examples that are commented-out in examples/check_examples.sh don't run successfully either with Python3 or with Python2. All examples that aren't commented-out run successfully with Python2 and Python3.

Please check "TO DEBUG" section at the end of examples/check_examples.sh script for the list of "broken" example scripts.