reexec under bash/ksh when possible #63

Add some code to the top of vimpager and vimcat to have the script
reexec itself, preserving redirection, under bash or ksh if available,
with the PATH modifies to find them on Solaris.

Both scripts need more work for better original bourne compatibility
aside from this hack.
fix copyright, add last 3 contributors

Remove duplicate copyright statement from vimcat I erroneously just
added.

Add the contributors for the last 3 pull requests.
require bash or ksh for vimcat, fix indents

Make the bash/ksh reexec fail if either one is not available in vimcat,
since the script uses arrays and will fail under plain bourne.

Fix the reexec code indents for the vimcat modeline.