Remove dead code.
style
Check in case the cursor's current node is NULL.
Don't need to check for null here. free(NULL) is okay, bro.
Small improvements to cursors and _ol_is_enabled.

- Fixes a bug zeroZshadow pointed out in regards to feature checking
- Cursors now fail to initialize if splay trees aren't enabled.
Fix travis failure.
Fixes bug when debug is enabled.
Separated lib install from frontend install