cmdline: cleanup option string definitions

cmdline: cleanup option string definitions

Option string composition has grown organically over time and is
depending on compilation options also. This results in somewhat complex
macro definitions and the use of the string concatenation feature of the
C compiler. This change tries to clean up some of this magic by removing
definitions of empty strings and merging of adjacent strings.

Change-Id: I968449ea9b564915bee468a0cac0e114983ceebe
Reviewed-on: https://code.wireshark.org/review/35429
Reviewed-by: Jaap Keuter <jaap.keuter@xs4all.nl>
Petri-Dish: Jaap Keuter <jaap.keuter@xs4all.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Gerald Combs <gerald@wireshark.org>