Add p4est feature query

[cburstedde]

Description

Similar to p4est_version_major, _minor, add a p4est_feature_query function.

Proposed solution

The feature query shall receive a const char * as input with a name matching any of the feature defines in p4est_base.h (btw. these defines need a more consistent naming scheme that shall be added). It will return 0 if the feature exists and -1 otherwise. The function will accept an extra int * argument that shall be -1 when feature is non-existent and non-negative when encoding additional information on an existing feature.