Implement rand/srand in terms of random/srandom.

Code developed for glibc or older versions of bionic might expect more
randomness than the BSD implementation provides.

Bug: 15829381

(cherry picked from commit 76c241b091b4d9d9a9237d40e814e52ce2917f47)

Change-Id: If721b3f16efdb21cb67df5ec5034c0ba905bd029
diff --git a/libc/Android.mk b/libc/Android.mk
index 1345159..51002e5 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -177,6 +177,7 @@
     bionic/pthread_sigmask.cpp \
     bionic/ptrace.cpp \
     bionic/raise.cpp \
+    bionic/rand.cpp \
     bionic/readlink.cpp \
     bionic/reboot.cpp \
     bionic/recv.cpp \
@@ -294,7 +295,6 @@
     upstream-netbsd/lib/libc/stdlib/mrand48.c \
     upstream-netbsd/lib/libc/stdlib/nrand48.c \
     upstream-netbsd/lib/libc/stdlib/_rand48.c \
-    upstream-netbsd/lib/libc/stdlib/rand.c \
     upstream-netbsd/lib/libc/stdlib/rand_r.c \
     upstream-netbsd/lib/libc/stdlib/seed48.c \
     upstream-netbsd/lib/libc/stdlib/srand48.c \