Add implementation for a64l

tests/stdlib/a64l.c

@@ -0,0 +1,22 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+int main(int argc, char* argv[]) {
+    char * s = "azAZ9."; // test boundaries
+    long l = a64l(s);
+    if (l != 194301926) {
+        printf("Invalid result: a64l(%s) = %ld\n", s, l);
+        return 1;
+    }
+    printf("Correct a64l: %s = %ld\n", s, l);
+
+    
+    s = "azA"; // test null terminated string
+    l = a64l(s);
+    if (l != 53222) {
+        printf("Invalid result: a64l(%s) = %ld\n", s, l);
+        return 1;
+    }
+    printf("Correct a64l: %s = %ld\n", s, l);
+    return 0;
+}