Camel case conversion for oneOf values does not correctly handle digits

[pavlo-triantafyllide-ck]

Camel case conversion for oneOf values does not correctly handle digits in the value name.

For example

message ShaValue {
    oneof value {
        Sha512WithRsa sha_512_with_rsa = 1;
        Sha256WithRsa sha_256_with_rsa= 2;
    }
}

is generated as:

{
  sha_512WithRsa: {}
  sha_256WithRsa: {}
}

but it should be:

{
  sha512WithRsa: {}
  sha256WithRsa: {}
}

I have a PR here to fix it
#2096

[pavlo-triantafyllide-ck]

looks like this is already an open issue: #1009 (comment)