BLI_assert: extract from BLI_utildefines

BLI_utildefines is quite large, defining many unrelated things.
Add BLI_assert to include in inline headers, so math defines don't
pull in too much.

source/blender/blenlib/BLI_math_base.h

@@ -35,6 +35,7 @@
 #endif
 
 #include <math.h>
+#include "BLI_assert.h"
 #include "BLI_math_inline.h"
 
 #ifndef M_PI