Fibonacci regex: Nasty length optimization that results in severe slowness; length-=10
Fibonacci regex: Capture other half along with remainder; length-=2
Fibonacci regex: Capture and reuse a leftover subtraction; length-=5
Fibonacci regex: Apply a dramatic speed optimization; length+=3
Fibonacci regex: Rename main version to reflect its intent
Fibonacci regex: Rename length-optimized version to reflect its intent
Merge branch 'length-optimized'