optionOnlyUsage - Print usage text for just the options
SYNOPSIS
#include <your-opts.h>
cc [...] -o outfile infile.c -lopts [...]
void optionOnlyUsage(tOptions* pOpts, int ex_code);
DESCRIPTION
This routine will print only the usage for each option.
This function may be used when the emitted usage must incorporate
information not available to AutoOpts.