Use # instead of = for ps2pdf options in Windows.

I couldn't get pstool to work under windows, because ps2pdf would fail with the error message: "**** Unable to open the initial device, quitting." Subsequently pdfcrop would also fail because its input file does not exist.

I eventually found this: http://ghostscript.com/doc/7.07/Use.htm#MS_Windows recommending the use of '#' instead of '=' for passing options to ghostscript via ps2pdf. Making this change and removing the quotes around the options for ps2pdf fixed the problem.
Use \filemodCmp rather than \pdf@strcmp to compare timestamps
Using \filemodCmp to check timestamps seems to work well. Merging.
update example doc
remove gmdoc; seems unstable :(
fix broken test for missing eps images
document bitmap options
document new \EndPreamble behaviour
use a preprocessor to switch = to # under windows

this should hopefully help out users a little more when they
add their own ps2pdf options