Reduce memory fragmentation cause by String usage. (#1536)
Reduce memory fragmentation cause by String usage. (#1536)

* Use more `.reserve()` to reduce fragmentation.
* Calculate some reservation values more accurately rather than flat guesses.

For #1493
markszabo/IRremoteESP8266,markszabo/IRremoteESP8266,markszabo/IRremoteESP8266,markszabo/IRremoteESP8266