Add Num.of_float_string that takes a decimal literal
Fix: strange index calculation in find, rfind
Add tests for split and rsplit
Fix: strange behaviour of nsplit and add tests.
Describe the situation where the separator is not found.
Fix docs (and code some) to remove nonstandard use of Invalid_rope in BatText
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/batText.ml