lib/contiki: drop some generic defines

Drop the MIN/MAX macros from the contiki includes. These can conflict
with other definitions, and are not used in the code.

Author: dlech

lib/contiki-core/sys/cc.h

@@ -134,18 +134,6 @@
 #define NULL 0
 #endif /* NULL */
 
-#ifndef MAX
-#define MAX(n, m)   (((n) < (m)) ? (m) : (n))
-#endif
-
-#ifndef MIN
-#define MIN(n, m)   (((n) < (m)) ? (n) : (m))
-#endif
-
-#ifndef ABS
-#define ABS(n)      (((n) < 0) ? -(n) : (n))
-#endif
-
 
 #define CC_CONCAT2(s1, s2) s1##s2
 /**