Explain what you would like to see improved

In TGCommandLinePlugin, pressing tab shows a list of options. It would be nice that, if there is only one option, it gets automatically 'pasted' into the text entry.

Optional: share how it could be improved

Parse and copy the content of the suggested code to the current text entry. (Removing the #Double_t stuff).

To Reproduce

1. On the plugin, type TMath::QuietN and press tab.
2. [#Double_t#]QuietNaN() is suggested as single option.
3. Ideally, the text entry would be now: TMath::QuietNaN() as it happens in a normal ROOT Terminal for the analogous case.

Setup

ROOT 6.25/01