* libc/stdlib/getenv.c: Delete "char *_findenv_r ();", as is not a
proper prototype, and is properly prototyped in stdlib.h, anyway.
* libc/stdlib/getenv_r.c: Ditto.
* libc/search/hash.c: Add _DEFUN to __hash_open() declaration; add
#define __DBINTERFACE_PRIVATE to activate prototypes from db_local.h.
* libc/search/db_local.h: Correct __hash_open() prototype.
* libc/sys/linux/cmath/math_private.h: Eliminate compiler warnings:
Remove #define INFINITY (redefines from math.h); remove #define __isnanf
and #define __isinff isinff.