title: strstr() function like, that ignores upper or lower case
body: <p>I have two strings. Lets say `</p>
  
  <pre><code>str1="One Two Three";
  </code></pre>
  
  <p>and </p>
  
  <pre><code>str2="two";
  </code></pre>
  
  <p>I would like to know if there is any function that checks for a match of the second string in the first one,and returns me a pointer to the first occurrence, something like <code>strstr()</code>, but which doesn't treat the same letter, upper or lowercase, as two different characters. </p>
  
  <p>For my example, the function should find a match for <code>str2</code> in the first string, despite the uppercase <code>"T"</code>, of <code>"Two"</code>.</p>