osc.c: Allow setting the capture timeout via .ini file

[dNechita]

There are scenarios where a larger timeout is needed. For example, when using the UART interface, the bandwith is significantly lower than USB or Ethernet. When "capture_timeout" is read from a .ini file, the assigned value (e.g. "capture_timeout=5000") will overwrite the value that osc computes internally.

[dNechita]

To add more details:
The logic used by osc to compute the timeout was like this:

• calculate how much time the hardware device would need to capture the samples. This is done by considering the sampling rate of the hardware and how many samples are set to be captured.
• add 1000 milliseconds to the time calculated above. This is to cover the time it would take the acquisition data to travel from the hardware over USB or Network.

But on some setups, where UART is being used and there is a larger number of samples to be transferred, the 1000 milliseconds don't even begin to cover the time needed for the samples to be sent over UART.