fix building main.cpp when readline is available
fix building main.cpp when readline is available

This changes around the pragma conditionals to make sure that certain
symbols (such as "default_search_path") are defined even if the system
has readline available during builds.

bradparks/ChaiScript__cplusplus_scripting_language,kamilzubair/ChaiScript,kamilzubair/ChaiScript,bradparks/ChaiScript__cplusplus_scripting_language,bradparks/ChaiScript__cplusplus_scripting_language,kamilzubair/ChaiScript