Define NDEBUG instead of SK_DEBUG/SK_RELEASE.

experimental/Intersection/QuarticRoot.cpp

 // from http://tog.acm.org/resources/GraphicsGems/gems/Roots3And4.c
 /*
  *  Roots3And4.c
  *
  *  Utility functions to find cubic and quartic roots,
  *  coefficients are passed like this:
  *
  *      c[0] + c[1]*x + c[2]*x^2 + c[3]*x^3 + c[4]*x^4 = 0
  *
  *  The functions return the number of non-complex roots and
@@ skipping 14 matching lines @@
  *                  than once.
  */
 
 #include    <math.h>
 #include "CubicUtilities.h"
 #include "QuadraticUtilities.h"
 #include "QuarticRoot.h"
 
 int reducedQuarticRoots(const double t4, const double t3, const double t2, const double t1,
         const double t0, const bool oneHint, double roots[4]) {
-#if SK_DEBUG
+#ifdef SK_DEBUG
     // create a string mathematica understands
     // GDB set print repe 15 # if repeated digits is a bother
     //     set print elements 400 # if line doesn't fit
     char str[1024];
     bzero(str, sizeof(str));
     sprintf(str, "Solve[%1.19g x^4 + %1.19g x^3 + %1.19g x^2 + %1.19g x + %1.19g == 0, x]",
         t4, t3, t2, t1, t0);
     mathematica_ize(str, sizeof(str));
 #if ONE_OFF_DEBUG && ONE_OFF_DEBUG_MATHEMATICA
     SkDebugf("%s\n", str);
@@ skipping 181 matching lines @@
                 if (j < --num) {
                     s[j] = s[num];
                 }
             } else {
                 ++j;
             }
         }
     }
     return num;
 }