Fix BIONIC_ROUND_UP_POWER_OF_2 for 64 bit.

There were two bugs here:

- For 64 bit values, this did not properly round up.
- The macro rounded to the power of 2 less than value, not to the power
  of 2 greater than value.

Change-Id: If8cb41536a9d2f5c1bc213676f1e67a7903a36b0

libc/private/bionic_macros.h

@@ -37,6 +37,8 @@
   (((value) + (alignment) - 1) & ~((alignment) - 1))
 
 #define BIONIC_ROUND_UP_POWER_OF_2(value) \
-  (1UL << (sizeof(value) * 8 - 1 - __builtin_clz(value)))
+  (sizeof(value) == 8) \
+    ? (1UL << (64 - __builtin_clzl(static_cast<unsigned long>(value)))) \
+    : (1UL << (32 - __builtin_clz(static_cast<unsigned int>(value))))
 
 #endif // _BIONIC_MACROS_H_