Added EvalMath library to COPYRIGHT

Added EvalMath library to COPYRIGHT.
As requested by @rdoursenaud

COPYRIGHT

@@ -26,6 +26,7 @@ php-iban               1.4.6         LGPL-3+                     Yes
 PHPPrintIPP            1.3           GPL-2+                      Yes             Library to send print IPP requests
 Restler                3.0           LGPL-3+                     Yes             Library to develop REST Web services
 TCPDF                  6.2.6         LGPL-3+                     Yes             PDF generation
+EvalMath               1.0           BSD                         Yes             Safe math expressions evaluation
 
 JS libraries:
 jQuery                 1.11.3        MIT License                 Yes             JS library