multiple doc issues for single_core

[Hermann-SW]

I am really interested in your repo.

The compile instruction misses to state that

• args.hxx needs to be installed into include path
• libssll-dev needs to be installed
• in additon -fopenmp needs to be on compile command line

Please provide a minimal example for eg. running single_core to produce a Charmichael number with 5 prime factors (like the minimal Charmichael number in your tables).

In case that differs for parallel, please provide am minimal example as well.
(I own a 192C/384T 8-socket server with 1TB RAM and would like to see what parallel will be able to do on my server!)

Simple examples for how to use of the other command line options would be good to have as well.

[drazioti]

I made some changes and I managed to compile it (the single core). In parallel there is a makefile.