Make CTRL+A select text in the current field

[kuchikuu]

Change the default behavior of CTRL+A from moving cursor to the beginning of the line, to selecting the whole text in the current field.
This is more intuitive for casual users and goes in pair with CTLR+X/C/V shortcuts.

Modified files:
dw/fltkui.cc <- shortcut inside the webpage
src/dialog.cc <- shortcut in a dialog (not tested)
src/fidnbar.cc <- shortcut in Search field
src/ui.cc <- shortcut in address bar

[kuchikuu]

Something that I wanted for a long time.

Edit: Come to think about it...
To select all text in address bar, you have to press CTRL+L (again)
to select all text in Find/Search bar, you have to press CTRL+F again

So I guess these two already had "select all" functionality.
But there's no way (at least that I know of) to select your text inside a website (for example in input field).

Well, up to you. Making CTRL+A select it as well, makes it more intuitive (I think).
Moving to the beginning of the line can also be achieved by CTRL+LeftArrow.

Edit2:
Ok, I don't know how to feel about this pull request anymore
It looks like there are ways to select text in a field inside a webpage.
We can press CTRL+SHIFT+Home after being at the end of the input field to select the whole text.

Well, I would like to be able to select everything in a field with a quick CTRL+A, but it's up to You to decide whether you want to merge it or not.