util/macros: Import ALIGN_POT from ralloc.c

v2 (Jason Ekstrand):
 - Rename y to pot_align (Brian)
 - Also use ALIGN_POT in build_id.c and slab.c (Brian)

Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/util/macros.h

@@ -285,6 +285,9 @@ do {                       \
 #define MIN3( A, B, C ) ((A) < (B) ? MIN2(A, C) : MIN2(B, C))
 #define MAX3( A, B, C ) ((A) > (B) ? MAX2(A, C) : MAX2(B, C))
 
+/** Align a value to a power of two */
+#define ALIGN_POT(x, pot_align) (((x) + (pot_align) - 1) & ~((pot_align) - 1))
+
 /**
  * Macro for declaring an explicit conversion operator.  Defaults to an
  * implicit conversion if C++11 is not supported.