cosmetics: remove arguments from main where they're unused

This prevents warnings about unused parameters (they're disabled by
default though, so they're not very visible).

src/bitbuffer.c

@@ -414,7 +414,7 @@ int bitbuffer_find_repeated_row(bitbuffer_t *bits, unsigned min_repeats, unsigne
 // Unit testing
 #ifdef _TEST
 #include <assert.h>
-int main(int argc, char **argv)
+int main(void)
 {
     fprintf(stderr, "bitbuffer:: test\n");
 

src/fileformat.c

@@ -290,7 +290,7 @@ void assert_str_equal(char const *a, char const *b)
     }
 }
 
-int main(int argc, char **argv)
+int main(void)
 {
     fprintf(stderr, "Testing:\n");
 

src/optparse.c

@@ -338,7 +338,7 @@ char *remove_ws(char *str)
         }                                                   \
     } while (0)
 
-int main(int argc, char **argv)
+int main(void)
 {
     unsigned passed = 0;
     unsigned failed = 0;

src/util.c

@@ -361,7 +361,7 @@ int add_nibbles(uint8_t const message[], unsigned num_bytes)
         } \
     } while (0)
 
-int main(int argc, char **argv) {
+int main(void) {
     unsigned passed = 0;
     unsigned failed = 0;