v20221220

There are quite a few changes here, please let me know if you see any problems.

New options -WW, -Ls, -Lf, -R:

• -WW<threshold> is the same as -W<threshold>, but stops after completing the first stage;
• -Ls<time> requests progress updates to the screen every <time> seconds, or no updates if time=0;
• -Lf<time> requests progress updates to the log file every <time> seconds, or no updates if time=0;
• -R disables recovery even if the log file already exists, useful to append runs for several patterns to the same file.

Selected bug fixes:

• Pell-like equations of the form x^2 - Dy^2 = N were not correctly solved if N had squared factors;
• extracting higher roots from lower roots (root_extract()) could return the wrong list of roots;
• minimum prime, maximum prime and -W threshold were all stored as 32-bit instead of 64-bit;
• -W was not correctly run for "tail" batches (which can be generated if -f is not set to the maximum possible).

New program pcaul:

• this is like pcoul but aimed at OEIS sequences A165498 and A165499 where the arithmetic progression has difference n instead of 1.

Thanks DemIS for the Windows build, attached as pcoul_20221220.zip.