change unsigned int to uint32_t for api arc4random/arc4random_uniform

Bug: 17894480
Change-Id: Ia4b5a7cd2b2c6002ed70955f86f7780d26d15e26
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index fd2bf6c..b97eaf9 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -112,8 +112,8 @@
 extern double drand48(void);
 extern void srand48(long);
 
-unsigned int arc4random(void);
-unsigned int arc4random_uniform(unsigned int);
+uint32_t arc4random(void);
+uint32_t arc4random_uniform(uint32_t);
 void arc4random_buf(void*, size_t);
 
 #define RAND_MAX 0x7fffffff