Added EV_TOSTR and EV_TOSTRLEN

Signed-off-by: Robear Selwans <robear.selwans@outlook.com>

tostr_test.c

@@ -0,0 +1,40 @@
+#include <stdio.h>
+#include "ev_types.h"
+#include "ev_numeric.h"
+
+typedef struct {
+  char *name;
+  int age;
+  char *desc;
+} Person;
+
+DEFINE_TOSTR_FUNCTION(Person, PERSON_PRINT)
+{
+  sprintf(out, "%s:\n\tage: %d\n\tdesc: %s", self->name, self->age, self->desc);
+}
+
+TYPEDATA_GEN(Person,
+    TOSTR(PERSON_PRINT),
+    DEFAULT(
+        .name = "sisyphus",
+        .age = 9999,
+        .desc = "One can only imagine him happy"
+    ),
+    INVALID(
+        .name = NULL,
+        .age = -1,
+        .desc = NULL
+    )
+);
+
+int main()
+{
+  puts("");
+  char out[256] = {};
+
+  Person sisyphue = EV_DEFAULT(Person);
+  EV_TOSTR(Person)(&sisyphue, out);
+
+  puts(out);
+  return 0;
+}