shell_print_commands() crashes

[joemcool]

Calling shell_print_commands() causes a crash. On my ESP8266 module, this manifests as a reboot with an exception cause of 3 (LoadStoreErrorCause). I believe this is caused by using PSTR() to store command strings in PROGMEM/flash, and then trying to print them with shell_println() instead of shell_println_pm(). I believe Arduino boards like the Uno and Mega would be affected by this as well, but don't have one to test with.

Steps to reproduce:
--Register a command with the command wrapped in a PSTR() call. e.g. shell_register(command_mycommand, PSTR("mycommand"));
--Call shell_print_commands()

I was using PSTR() because its what is done in the examples, and seems to be what the library expects. I have plenty of RAM available on my module, so I've moved away from the PSTR() calls as a temporary solution and things are working. However, it seems cleaner to fix this issue by adding an #ifdef ARDUINO wrapper to the shell_print_commands() function's loop so that the correct print_ln function gets called.