Rename custom variant with gil_ prefix. Do not define project ID from Jamfile-s as unnecessary. The project ID-s and build features are global resources, easy to clash. Add recently added test/ subdirectories to build.
Update examples to catch up with recent changes and ensure they both compile without errors (using GCC 5).
Rename Jamfile.v2 to Jamfile - BBV1 is dead. Remove numeric/test/test.cpp as redundant.
