Add support for larger message size

[chubby077]

Is your feature request related to a problem? Please describe.
I am working to send json log data via syslog using Posh-SYSLOG. Sometimes the messages are longer than 2048 bytes. Although this is not standard size for syslog, some endpoints support larger messages.

Describe the solution you'd like
I can make it work by updating the module to allow for 4096 byte messages. Adding a flag for larger messages or possibly specific maximum message size would allow for these cases.

Examples of how the solution would work
Setting the RFC5424 section to maxlength of 4096 handles the cases I've run into. A flag to either use non-standard size or specify max length would address this.