Add/enhance timl.core vars

# Notes

- changed `unchecked-inc` to `inc`
- changed `long` to `int`

# Enhance

- multi-arity map

# Add

- mapv
- min-key
- merge-with
- doseq
- dotimes
- when-first
- lazy-cat
- mapcat
- take-while
- drop-last
- take-last
- drop-while
- cycle
- split-at
- split-with
- nthrest
- take-nth
- interleave
Merge pull request #8 from frenchy64/core-fns

Add/enhance timl.core vars