ptime -p could support multiple processes
Currently ptime -p only supports one process. Furthermore, the implementation and documentation do not match its usage. Specifically the documentation implies that -m must come before -p. However, in reality this is not the case and many people might use ptime -p $$ -m. As a result, we can't quite mimic the other ptools exactly here; however, ptime itself already has an odd construction in that it tries to match time(1) more so. To handle this we instead just allow -p to optionally take a comma separated list of processes and report information about all of them.