Adding timeout parameter to testrunner

[apaikan]

It will be very useful to have timeout for running the tests using testrunner.

Problem

As it is for now, if one of the test cases gets blocked, the testrunner is blocked too and no more tests are running until the CTRL+C is pressed from the testrunner terminal.

Suggestion

1. to add --timeout <seconds> param to the testrunner
2. Add the `timeout' property /tag to the test suite xml file:

<?xml version="1.0" encoding="UTF-8"?>

<suit name="my suit">
    <description> a simple example </description>

   <!-- default timeout for all tests -->
    <timeout> 5.0 </timeout>

    <test type="dll"> mytest2 </test>
   ...
   
   <!-- timeout for a specific test -->
    <test type="dll" timeout="10.0"> mytest1 </test>
    ...
</suit>

[apaikan]

Is this issue still major? @valegagge what do you think? :)