block zero analysis is likely to fail for small blocksz

[jtmoon79]

Problem

A small --blocksz, the smallest in release builds is 0x40, may cause failure during SyslogProcessor::blockzero_analysis_lines.

Solution

Refactor the blockzero_analysis_lines approach.

[jtmoon79]

There is two connected issues that currently occur for any sized block:

• the minimal Sysline count to pass is too small, not enough confidence in chosen DateTimeParseInstr
  https://github.com/jtmoon79/super-speedy-syslog-searcher/blob/0.1.45/src/readers/syslogprocessor.rs#L135-L146

• after the final DateTimeParseInstr is chosen, any Syslines processed with any other DateTimeParseInstr must be reprocessed (the entire Block would need to be reprocessed). In other words, if any currently stored Sysline was processed using a different DateTimeParseInstr than all of the Syslines must be removed (do not drop them), and then the entire zero Block must be reprocessed for Syslines (luckily, should be fast as the Block and all Lines are still valid). Similar to what is done for reprocessing for missing years. (moved this into Issue block zero analysis needs reprocessing step #74 )