Define starflate::{copy,copy_n}

[oliverlee]

starflate::{copy,copy_n} are variants of the standard library copy
and copy_n algorithms but modified for use in DEFLATE decoding. Both
of these algorithms specifically handle overlap of the source and
destination ranges.

starflate::copy_n takes an input iterator, distance, and output
iterator,

starflate::copy takes a source range and a destination range,
returning the unwritten subrange of the destination range.

Change-Id: I756a8416a82f4a2007c7f2461de04353aac667d6

[oliverlee]

Not sure if this is the right place for this header since I don't imagine copy_n to be part of the public interface of starflate or decompress.

[codecov]

Codecov Report

Merging #109 (c2cd62a) into master (87d0405) will decrease coverage by 1.27%.
The diff coverage is 70.83%.

@@            Coverage Diff             @@
##           master     #109      +/-   ##
==========================================
- Coverage   58.98%   57.72%   -1.27%     
==========================================
  Files          12       13       +1     
  Lines         885      965      +80     
==========================================
+ Hits          522      557      +35     
- Misses        363      408      +45     

Files	Coverage Δ
src/copy.hpp	70.83% <70.83%> (ø)

... and 1 file with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[oliverlee]

I think this is the wrong approach and I'll update with a different design later.

[garymm]

Do you want me to review? If not mark as draft please

[oliverlee]

Do you want me to review? If not mark as draft please

nope don't review, i'm going to change this at some point