This first patch makes only trivial changes.  Excess whitespace at the end
of lines is removed and return codes are altered from -1 to symbolic error
values.  The only significant difference is that in one spot a valid
return is changed to an error return, when a descriptor does not have the
correct type.

 - Remove excess whitespace at the ends of lines.
 - Change return codes to symbolic values.
 - Return an error when an invalid endpoint descriptor is found.