test: don't use wiki urls for documentation comments

Also make consistent use of \ as documentation escape character.

src/test/SDL_test_fuzzer.c

@@ -161,7 +161,7 @@ SDLTest_RandomIntegerInRange(Sint32 pMin, Sint32 pMax)
     return (Sint32)((number % ((max + 1) - min)) + min);
 }
 
-/* !
+/**
  * Generates a unsigned boundary value between the given boundaries.
  * Boundary values are inclusive. See the examples below.
  * If boundary2 < boundary1, the values are swapped.
@@ -288,7 +288,7 @@ SDLTest_RandomUint64BoundaryValue(Uint64 boundary1, Uint64 boundary2, SDL_bool v
                                                   validDomain);
 }
 
-/* !
+/**
  * Generates a signed boundary value between the given boundaries.
  * Boundary values are inclusive. See the examples below.
  * If boundary2 < boundary1, the values are swapped.

src/test/SDL_test_log.c

@@ -46,7 +46,7 @@ strftime_gcc2_workaround(char *s, size_t max, const char *fmt, const struct tm *
 #define strftime strftime_gcc2_workaround
 #endif
 
-/* !
+/**
  * Converts unix timestamp to its ascii representation in localtime
  *
  * Note: Uses a static buffer internally, so the return value