Do I need those two libraries for anything?
Only you could know that. (BUT - those extensions are probably deprecated and/or replicated by PEAR/PECL/Zend components anyway).
The 'right answer' is to Google them, and read what the function/extension does. I'm pretty sure the php_pdf.dll is for PDF output. mime_magic is deprecated in favor of filesinfo. If you need to do PDF ourput, you should look for a PHP function in the libraries included with the current XAMPP version.
I can shed light on one or two other things for you.
ts.dll is the primary PHP component/module that Apache calls. The X is the version number, and the 'ts' is for 'thread safe' (the only option for Win32 Apache). So as Wole pointed out, its not relevant to PHP 5 installations.
(dlls) are version specific (as to PHP) and must be compiled with the same compiler used for Apache (at least in XAMPP for Windows installations). Thus many 'foreign extensions' just won't work, or throw errors.