fix feature detection

Author: minad

demo/test.c

@@ -61,25 +61,25 @@ void does_not_exist(void);
 
 static int test_feature_detection(void)
 {
-#define BN_TEST_FEATURE1_C
+#define TEST_FEATURE1_C
    if (!MP_HAS(TEST_FEATURE1)) {
       does_not_exist();
       return EXIT_FAILURE;
    }
 
-#define BN_TEST_FEATURE2_C 1
+#define TEST_FEATURE2_C 1
    if (MP_HAS(TEST_FEATURE2)) {
       does_not_exist();
       return EXIT_FAILURE;
    }
 
-#define BN_TEST_FEATURE3_C 0
+#define TEST_FEATURE3_C 0
    if (MP_HAS(TEST_FEATURE3)) {
       does_not_exist();
       return EXIT_FAILURE;
    }
 
-#define BN_TEST_FEATURE4_C something
+#define TEST_FEATURE4_C something
    if (MP_HAS(TEST_FEATURE4)) {
       does_not_exist();
       return EXIT_FAILURE;

tommath_private.h

@@ -143,7 +143,7 @@ extern void MP_FREE(void *mem, size_t size);
 /* feature detection macro */
 #define MP_STRINGIZE(x)  MP__STRINGIZE(x)
 #define MP__STRINGIZE(x) ""#x""
-#define MP_HAS(x)        (sizeof(MP_STRINGIZE(BN_##x##_C)) == 1)
+#define MP_HAS(x)        (sizeof(MP_STRINGIZE(x##_C)) == 1)
 
 /* TODO: Remove private_mp_word as soon as deprecated mp_word is removed from tommath. */
 #undef mp_word