Some implementation details are dictated by Kotlin/Native shortcomings

[dkhalanskyjb]

• In several places, x in A..B is replaced with the non-idiomatic x >= A && x <= B. This is due to the fact that Kotlin/Native does not yet optimize such constructs outside of for-loops. In particular, in LocalTime#ofSecondOfDay about half the time of the function execution was spent in argument validity checks, allocating several objects in the meantime. https://youtrack.jetbrains.com/issue/KT-38787
• Parsers are not singleton objects but are instead functions that return newly-constructed parsers. This is done to sidestep a bug that led to an unchecked null value dereferencing as a result of wrong initialization order of values: parser A, referencing parser B, was being initialized before B, which led to it dereferencing a null value.