API Feature - api.HasFunction Check

- Allows querying the featureset of an API without calling the function
- Avoids some exceptions or unwanted behaviour
- Avoids false negatives from using "if (api.Call( name, func ))" when valid return value is false
API Feature - api.HasFunction Check, rev2

- Allows querying the featureset of an API without calling the function
- Avoids some exceptions or unwanted behaviour from Call-ing to test
- Returns true if function exists, false if it doesn't (or if the API is not found).
Merge pull request #31 from Gliktch/patch-1

API Feature - api.HasFunction Check