- enables partial overwriting of content
- make default construct zero-sized, add reserve_exact() method
- improve sizing behaviour of OCharStream.
Since char buffers will approach the INT_MAX size more quickly than
other content, adapt the following strategy:
| Capacity range | Strategy |
|--------------------|------------------------------|
| 0 < N <= 0.25) | fast growth (2) |
| 0.25 < N <= 0.5) | slower growth (1.5) |
| 0.5 < N <= 0.75) | very slow growth (1.25) |
| 0.75 < N | already large - use max |
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