(cherry picked from commit 7ccf903ee3d9da4a104310ed423130857d59d91b)

(cherry picked from commit 2b40e2906fc070c6253a84c0ca507ff0db912f73)

(cherry picked from commit 474ec252a23745bf5106b239054c17d7dfc2fbf2)

(cherry picked from commit 3eb7b6bfbde6a847154c6053e7b4171554207865)

(cherry picked from commit cbdd9202)

(cherry picked from commit 2e09a8f4)

(cherry picked from commit d3cea8a4)

(cherry picked from commit bb0f033b)

(cherry picked from commit d2ea5a48)

Due to using QTextCursor::columnNumber() instead of
QTextCursor::positionInBlock(), a lot of code would not work correctly
when used with wrapped lines.

In addition, there was an issue with columnNumber() returning 0 right
after inserting a character before the last character of a line.

Reviewed-by: mae

On Mac, QKeyEvent::text() returns non-empty strings for cursor keys. This
breaks some of the logic relying on text() being empty for "special" keys.

This is a quick fix to make it usable.

In theory this should have been a backport of the search-related commits
7e8c345a and 46fa3aa7, but they are buried in the middle of the Big
Commandline Reorganization. Just taking everything has lower risk and
is faster.

Reviewed-by: ossi

Reviewed-by: hjk

Discussed-with: hjk

The Parentheses, TextBlockUserData and TextEditDocumentLayout classes
and their member function implementations were spread around the
BaseTextEditor class. Moving them to their own file to make the code a
bit better organized.

Reviewed-by: mae