bpo-35674: Add os.posix_spawnp() (GH-11554)

Add a new os.posix_spawnp() function.
diff --git a/configure b/configure
index 13677b9..b32481d 100755
--- a/configure
+++ b/configure
@@ -11447,7 +11447,7 @@
  initgroups kill killpg lchown lockf linkat lstat lutimes mmap \
  memrchr mbrtowc mkdirat mkfifo \
  mkfifoat mknod mknodat mktime mremap nice openat pathconf pause pipe2 plock poll \
- posix_fallocate posix_fadvise posix_spawn pread preadv preadv2 \
+ posix_fallocate posix_fadvise posix_spawn posix_spawnp pread preadv preadv2 \
  pthread_init pthread_kill putenv pwrite pwritev pwritev2 readlink readlinkat readv realpath renameat \
  sem_open sem_timedwait sem_getvalue sem_unlink sendfile setegid seteuid \
  setgid sethostname \