These changes to the functions epicsStrnRawFromEscaped() and
epicsStrnEscapedFromRaw() were prompted by the addition of JSON5
support to the dbStatic parser.
* \0 now represents a zero byte
* Unprintable characters are now escaped in hex
Tests for the octal escapes have been removed.
\x only takes 2 hex digits now, and the octal parser ignores a 3rd
digit if it would take the value over 0xff:
"\400" => ' ' then '0'
"\x088" => '\b' then '8'
With additional tests.
In some cases the license-identification header was missing,
so I added that as well. Replaced the remaining headers that
specifically identified "Versions 3.13.7 and higher".
Makefiles and the build system were deliberately excluded.
