includes workaround for breakage with old g++

This reverts commit a05ba6fd.

Fixed the actions but broke handling of Esc-key and navigating to line numbers in locator bar.

Only revert stuff that is linked to fast string concat.

Reviewed-by: kh1

This reverts commit e70530c5. It
did break builds on older gcc versions (gcc 4.1.2 64 bit Linux,
gcc 4.0.1 on Mac OS X):

parser/qmljsgrammar_p.h: In static member function ???static int
QmlJSGrammar::nt_action(int, int)???:
parser/qmljsgrammar_p.h:188: error: ???QmlJSGrammar::<anonymous enum>???
is/uses anonymous type
parser/qmljsgrammar_p.h:188: error:   trying to instantiate
???template<class T> struct QConcatenable???
...

Change it into a singleton that listens for device changes
and emits signals when devices are added or removed.

Merge-request: 1949
Reviewed-by: Thorbjørn Lindeijer <thorbjorn.lindeijer@nokia.com>

Reviewed-by: Oswald Buddenhagen

TODO: only transfer deltas

this makes the i/o part of the evaluator thread-safe.
for safety, assert absolute paths in IoUtils::exists().

on the way, i "stole" some code i wrote for KDE. there have been no
copyright-worthy contributions from others to it, so this is legal.

somewhat faster again

now items have no vtable any more

it's overengineered for our purpose and would just get in the way of
planned optimizations.

use a hash of magic variable names to ints, which allows fast lookup
followed by a jump table dispatch