Miscellaneous small DNS resolver updates and fixes

This pull request contains three patches which address:

 * Failure to compile with SDCC. (639a9ca399d132855f5577c0b64f5a4d4786b16e)
 * `CNAME` records do not resolve correctly. (7e9f472faab68024cf5dcf75126f547e48927017)
 * A handful of minor updates and clarifications. (da81360731a0f1d96d945762d37fc81a8ed27d77)