XER field size issue for ENUMERATED

[tkillian7]

In the following enumeration:

Compression-Type ::= ENUMERATED {
    none(0),
    zlib(1),
    lzma(2),
    reserved(15)
}

The code that generates REQUIRED_BYTES_FOR_XER_ENCODING in the header file, produces a value that is too small, causing test cases to fail.

The line below compares the strings in the enumeration, not the length of the strings. Since 'z' is greater than 'r', 'zlib' is returned, rather than the longest string, which is 'reserved'.

https://github.com/maxime-esa/asn1scc/blob/9d0db14ea8d6cbe10189e3f02803f2caf3455166/BackendAst/DAstXer.fs#L49