pru: Do not define MISSING_SYSCALL_NAMES for pru

- The PRU newlib port is supposed to implement case #2 as described in
  newlib/libc/include/reent.h .  Thus drop the defining of
  MISSING_SYSCALL_NAMES.
- libgloss/configure: Regenerate.
- libgloss/libnosys/acinclude.m4: Do not define
  MISSING_SYSCALL_NAMES for pru.

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>

libgloss/configure

@@ -5349,6 +5349,7 @@ case "${target}" in
   mn10?00-*-*) ;;
   riscv*-*-*) ;;
   powerpcle-*-pe) ;;
+  pru-*-*) ;;
   sh*-*-*) ;;
   sparc-sun-sunos*) ;;
   sparc64-*-*) ;;

libgloss/libnosys/acinclude.m4

@@ -16,6 +16,7 @@ case "${target}" in
   mn10?00-*-*) ;;
   riscv*-*-*) ;;
   powerpcle-*-pe) ;;
+  pru-*-*) ;;
   sh*-*-*) ;;
   sparc-sun-sunos*) ;;
   sparc64-*-*) ;;