ecpg: avoid adding whitespace around '&' in connection URLs.

ecpg: avoid adding whitespace around '&' in connection URLs.

The preprocessor really should not have done this to begin with.
The space after '&' was masked by ECPGconnect's skipping spaces
before option keywords, and the space before by dint of libpq
being (mostly) insensitive to trailing space in option values.
We fixed the one known problem with that in 920d51979.  Hence
this patch is mostly cosmetic, and we'll just change it in HEAD.

Discussion: https://postgr.es/m/TY2PR01MB36286A7B97B9A15793335D18C1772@TY2PR01MB3628.jpnprd01.prod.outlook.com