Prevent assignments in assertions

Using the else branch instead of explicitly negating the assertion makes
sure the compiler catches assignments in assertion expressions.

maxutils/maxbase/include/maxbase/assert.h

@@ -24,7 +24,7 @@ MXB_BEGIN_DECLS
 #if defined (SS_DEBUG)
 
 #define mxb_assert(exp) \
-    do {if (!(exp)) { \
+    do {if (exp) {} else { \
             const char* debug_expr = #exp;      /** The MXB_ERROR marco doesn't seem to like stringification
                                                  * */ \
             MXB_ERROR("debug assert at %s:%d failed: %s\n", (char*)__FILE__, __LINE__, debug_expr); \
@@ -32,7 +32,7 @@ MXB_BEGIN_DECLS
             raise(SIGABRT);}} while (false)
 
 #define mxb_assert_message(exp, message) \
-    do {if (!(exp)) {     \
+    do {if (exp) {} else {     \
             const char* debug_expr = #exp; \
             MXB_ERROR("debug assert at %s:%d failed: %s (%s)\n", \
                       (char*)__FILE__, \