do not close braces automatically on enter if the next line's indentation
is deeper than the current line's

Introduced T_CPP_COMMENT and T_CPP_DOXY_COMMENT to handle C++-style comments and improved CPPEditor::isInComment to handle the newly introduced tokens.

As side effect,this change should fix the regression we introduced in the "automagically" quote/brace insertion.

We now exclude brace in ifdefed out sections when calculating,
whether or not the braces match. This requires adjust the brace
levels whenever sections get ifdef'd out or ifdef'd in again.

When inserting or deleting ( or [, we now check wether this will improve
the block's parentheses balancing, and only fix it if it doesn't. Same
applies to skipping of ) or ].

This reverts commit 6b510cb4.

only set the background, we do not want to modify foreground properties
set by the syntax highlighter or the link

remove some standard actions from the cpp editor context menu,
and enhance the advanced menu instead.

Add `Find References' of a symbol to the context menu only when the environment variable QTCREATOR_REFERENCES is defined.

CPPEditor::isInComment() returns if the text cursor is in a comment.

Need to check the character to the right of the cursor.

Cause that's the relevant context.

Done with mae and Roberto Raggi.

Done with mae.

its only turned on in the cpp editor.