allow compilation using -Wall -Werror

[rursprung]

currently the build fails with the following errors when including pigpio.h from a project which uses -Wall -Werror:

In file included from .../foo.cpp:1:
.../pigpio.h:4528:6: error: "/*" within comment [-Werror=comment]
 4528 | /home/* n
      |
.../pigpio.h:4529:22: error: "/*" within comment [-Werror=comment]
 4529 | /home/pi/shared/dir_1/* w
      |
.../pigpio.h:4530:22: error: "/*" within comment [-Werror=comment]
 4530 | /home/pi/shared/dir_2/* r
      |
.../pigpio.h:4531:22: error: "/*" within comment [-Werror=comment]
 4531 | /home/pi/shared/dir_3/* u
      |
.../pigpio.h:4584:11: error: "/*" within comment [-Werror=comment]
 4584 |    // /ram/*.c r
      |
.../pigpio.h:4740:11: error: "/*" within comment [-Werror=comment]
 4740 |    // /ram/*.c r
      |

it seems that this should be fairly simple to fix (just adapt the comment) but i decided against providing a PR as the comments carry some meaning (they show paths) and i'm not familiar with this code, so i'm unsure what the best replacement would be.