add two tests

test/stralloc_buffer.c

@@ -0,0 +1,10 @@
+#include "stralloc.h"
+#include "buffer.h"
+
+main() {
+  static stralloc sa;
+  if (buffer_get_token_sa(buffer_0,&sa," \t\n",3)==0) {
+    buffer_putsa(buffer_1,&sa);
+    buffer_putnlflush(buffer_1);
+  }
+}