Symbol expansion problem in strxxx function

Summary

When testing the rcconf01 example in aarch64 mode with cpu memory in the range 0x80000000-0x90000000, since rtems-bsd-rc-conf.c does not include string.h, This causes symbol extension problems when calling functions such as strdup and strchr, which can cause system crashes.

This problem also exists in rtemsbsd/ftpd/ftpd-service.c and rtemsbsd/rtems/rtems-routes.c.

Some warnings were raised at compile time:

Steps to reproduce

Aarch64 mode, cpu memory in the range 0x80000000-0x90000000, run rtems-libbsd/testsuite/rcconf01/test_main.c example.

Steps to resolve

Add #include <string.h> in these files.