Add pthread_rwlock_t implementation to the C library (DO NOT MERGE)

Change-Id: I756d8c26afc37cd7b71117ddbaa02a2cb40fdecb
diff --git a/libc/Android.mk b/libc/Android.mk
index 590afbe..0271f10 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -322,6 +322,7 @@
 # up any thumb code.
 libc_common_src_files += \
 	bionic/pthread.c.arm \
+	bionic/pthread-rwlocks.c.arm \
 	bionic/pthread-timers.c.arm \
 	bionic/ptrace.c.arm
 
@@ -356,6 +357,7 @@
 	arch-x86/string/strncmp_wrapper.S \
 	arch-x86/string/strlen.S \
 	bionic/pthread.c \
+	bionic/pthread-rwlocks.c \
 	bionic/pthread-timers.c \
 	bionic/ptrace.c
 
@@ -393,6 +395,7 @@
 	string/strlen.c \
 	bionic/eabi.c \
 	bionic/pthread.c \
+	bionic/pthread-rwlocks.c \
 	bionic/pthread-timers.c \
 	bionic/ptrace.c \
 	unistd/socketcalls.c