* libc/stdlib/envlock.c: changed documented "__env_lock" and
"__env_unlock" prototype from "void *" or "char *" to
"struct _reent *" to match real function. Also added include
of envlock.h.
* libc/stdlib/mlock.c: changed documented "__malloc_lock" and
"__malloc_unlock" prototype from "void *" or "char *" to
"struct _reent *" to match real function.
* libc/stdlib/envlock.h: added "__env_lock" and "__env_unlock"
prototypes (for getenv_r.c and setenv_r.c).
