eglfs: Upload only damaged areas into the textures

Uploading the pixel data for the entire window on every update
is not nice. Not sure why the line in question was added, it is
most likely a leftover from some debugging session.

Change-Id: I161af536c42ac24b299fc674039f2318f0fb8c4f
Reviewed-by: Andy Nichols <andy.nichols@digia.com>
eglfs: Fix physical screen size regression for some hooks

On boards that provide their own custom ways of querying the screen size
the resolution of widget apps became somewhat incorrect after the recent
eglfs/eglconvenience refactor. This is because the physical size query
helper was not able to access the screenSize() provided by the hooks,
it was instead falling back to the default fb query which in turn returned
the default screen size (e.g. 800x600).

Change-Id: I46d487b61341d69dd9cb76d93198b1f44b64f195
Reviewed-by: Andy Nichols <andy.nichols@digia.com>
Disable terminal keyboard on eglfs and linuxfb

Unify the behavior for eglfs, linuxfb and kms. The relevant code is
now moved from kms into fbconvenience.

From now on, on all three platforms, terminal keyboard input is turned
off by default. This feature can be disabled by setting
QT_QPA_ENABLE_TERMINAL_KEYBOARD to 1. This is similar to what the
evdev-based keyboard handler did in QWS in Qt4.

[ChangeLog][QtGui] The main Embedded Linux platform plugins (eglfs,
linuxfb, kms) are changed to behave identically with regards to
terminal keyboard input: it is turned off by default on all of these
platforms. If this feature is not desired, it can be disabled by
setting the environment variable QT_QPA_ENABLE_TERMINAL_KEYBOARD.

Task-number: QTBUG-36394

Change-Id: I69e47ed7580464dc5e703e9a0e23891c7c8b7790
Reviewed-by: Andy Nichols <andy.nichols@digia.com>