Various mount fixes

The current `mount` core type has open issues (some are a couple of years old) and this pull request attempts to fix some of them. I am fully aware of the "split the mount type in mounttab and mountpoint"-project (http://projects.puppetlabs.com/issues/7188) but I don't see any activity to merge this into core.

So I'd rather see these fixes merged even though they might become obsolete in the future.

This patchset includes fixes for
- http://projects.puppetlabs.com/issues/6409 (Mount provider should reject spaces in fstab fields)
- http://projects.puppetlabs.com/issues/4689 (mount resource for nfs share gives error)
- http://projects.puppetlabs.com/issues/6793 (mount provider fails when paths have a trailing slash)
- http://projects.puppetlabs.com/issues/21168 (mount property "pass" should default to "-" on Solaris)
- http://projects.puppetlabs.com/issues/15837 (mount with options specified on Linux)
- http://projects.puppetlabs.com/issues/7791 (puppet should reject certain options when running mount -o)