Fix a preprocessor defect, where nested dead #if-#endif had nesting depth off by one level, turning what should be dead code into live code.

git-svn-id: https://cvs.khronos.org/svn/repos/ogl/trunk/ecosystem/public/sdk/tools/glslang@20461 e7fa87d3-cd2b-0410-9028-fcbf551c1848

Test/cppNest.vert

@@ -38,6 +38,16 @@ sum += 50000.0;
         sum += 0.2;
     #endif
 
+    //no
+    sum += 0.01;
+    #ifdef ON
+        //no
+        sum += 0.02;
+    #else
+        //no
+        sum += 0.03;
+    #endif
+
 //no
     sum + 0.3;