Compililation with gcc (any version) and Qt 5.12.0 (important) fails with error:
```
Core/private/sysapiloader_p.h:59:26: error: no matching function for call to ‘QMutex::QMutex()’
static inline QMutex m_mutex;
^~~~~~~
include/QtCore/qmutex.h:165:5: note: candidate: ‘QMutex::QMutex(const QMutex&)’ <deleted>
Q_DISABLE_COPY(QMutex)
^~~~~~~~~~~~~~
```
`QMutex` in Qt 5.12.0 has explicit (!) one-parameter constructor with a
default value: `QMutex(QMutex::RecursionMode mode = NonRecursive)` and no
default constructor. In this case declaring static inline member without
initializer causes the above error.
1. Added WindowBorderPainter for QtWidgets
2. Added WindowBorder for QtQuick (uses WindowBorderPainter internally)
3. Adjust some header includes
4. Limit a Linux workaround to the appropriate Qt versions
Signed-off-by: Yuhang Zhao <2546789017@qq.com>
TODO:
1. Special handling for the close button
2. Move QuickChromePalette class to own files
3. More testing
Signed-off-by: Yuhang Zhao <2546789017@qq.com>