mrand48 broken on 64-bit systems

[enh <enh%google.com@localhost>]

The mrand48() and jrand48() functions return signed long integers
uniformly distributed over the interval [-2**31,2**31].
http://pubs.opengroup.org/onlinepubs/7990989799/xsh/drand48.html

the freebsd, netbsd, and openbsd mrand48 implementations all just
assume that long is 32-bit, and are thus broken on 64-bit
architectures. (found running Android's bionic unit tests on x86_64.)

a cast appears to be all that's missing (though i don't know whether
you support architectures where sizeof(int) != 4, in which case you'll
want int32_t instead):

diff --git a/libc/upstream-netbsd/libc/stdlib/mrand48.c
b/libc/upstream-netbsd/libc/stdlib/mrand48.c
index c787ce6..b1083a1 100644
--- a/libc/upstream-netbsd/libc/stdlib/mrand48.c
+++ b/libc/upstream-netbsd/libc/stdlib/mrand48.c
@@ -29,5 +29,5 @@ long
 mrand48(void)
 {
  __dorand48(__rand48_seed);
- return ((long) __rand48_seed[2] << 16) + (long) __rand48_seed[1];
+ return (int) ((long) __rand48_seed[2] << 16) + (long) __rand48_seed[1];
 }