Add simple versions of random() and srandom()

Add simple versions of random() and srandom()

Prototypes also added for initstate() and setstate() but they
were not implemented in the shared newlib code.

	* newlib/libc/include/cygwin/stdlib.h: Prototypes added.
	* winsup/cygwin/include/cygwin/stdlib.h: Prototypes removed.
	* newlib/libc/stdlib/random.c: New file.
	* newlib/libc/machine/epiphany/machine/stdlib.h: Removed
	* newlib/libc/stdlib/Makefile.am: Added random.c.
	* newlib/libc/stdlib/stdlib.tex: Added random.def.
	* newlib/libc/stdlib/Makefile.in: Regenerated.