… get around issues related to using raw pointers and pointer arithmetic

…parently one step before using from_chars recently added to falco namespace in falco_utils.hpp

…get_next function to work with iterators instead of pointers as samrec::pos_t

…light associated cost, because samrec::pos_t is iterators and not raw pointer

…rs. Resetting those iterators in the reset function for sam_file class

…iterators as samrec::pos_t

…s to iterators in the bamrec class and free function accessors

…erator and const_iterator types

…for extracting isize

…e file

…iwyu

…ting from falco::from_chars to std::from_chars

…ent a tautology when comparing with 255. Now get_next for samrec has types specified

…removed span

… types in function signatures, moved definition of core_t to bam_core_t out of bamrec class and removed core_t member as it was only ever used in a narrow scope within one function

…al SAM records because I don't understand why the performance characteristics change so dramatically. Leaving this issue for next time.