Do not use strlcpy and strlcat

They are not standard yet.  Better for now to avoid them.

src/goxel.h

@@ -242,11 +242,6 @@ static inline float smoothstep(float edge0, float edge1, float x)
     return x * x * (3.0f - 2.0f * x);
 }
 
-// Fallback for strlcpy if it doesn't exists.
-#ifndef strlcpy
-#define strlcpy(dst, src, size) snprintf(dst, size, "%s", src)
-#endif
-
 /*
  * Function: mix
  * Linear blend of x and y.

src/main.c

@@ -302,22 +302,24 @@ static void split_path_and_file(
 
     sep = strrchr(path_and_file, '/');
     if (!sep) {
-        strlcpy(path, path_and_file, path_size);
-        file[0] = '\0';
+        snprintf(file, file_size, "%s", path_and_file);
+        path[0] = '\0';
     } else {
         path_len = (int)(sep - path_and_file);
         snprintf(path, path_size, "%.*s", path_len, path_and_file);
-        strlcpy(file, sep + 1, file_size);
+        snprintf(file, file_size, "%s", sep + 1);
     }
 }
 
 static void filters_to_nfd_spec(
         const char *const *filters, char buf[], size_t buf_size)
 {
     int i;
+    size_t len = 0;
+
     buf[0] = '\0';
     for (i = 0; filters[i]; i++) {
-        strlcat(buf, filters[i] + 2, buf_size);
+        len += snprintf(buf + len, buf_size - len, "%s", filters[i] + 2);
     }
 }
 
@@ -356,7 +358,7 @@ static bool open_dialog(
                 &(nfdsavedialogu8args_t){
                     .filterList = &filter,
                     .filterCount = 1,
-                    .defaultPath = default_path,
+                    .defaultPath = default_path[0] ? default_path : NULL,
                     .defaultName = default_name,
                     .parentWindow = nfd_window,
                 });