Changing payas/remove-extra-whitespace to only remove whitespace.

This function kept clobbering some characters in the last parameter like quotes and brackets so I rewrote it to only remove whitespace.

It also removes a trailing comma from the last parameter, if it
exists.

Some newly supported cases:

    foo('quoted'  )
    foo("quoted", )
    foo($var,  )
    foo($foo, bar() )