package/qt5: bump latest version to 5.9.1

package/qt5: bump latest version to 5.9.1

Qt 5.9 is a Long Term Support version [1]. Some license file changes are
involved, a new dependency on pcre2, and some filename changes.  qt5webkit
popped back into the picture for 5.9.1 after being absent for 5.9.0
"officially." QT5_SNAPSHOTS_SITE is removed with this commit as it is not used
for qtwebkit anymore.

This removes the following patches that have been upstreamed for 5.9.1:

- qt5base/5.8.0/0001-fix-parallel-builds-with-qt-freetype-system-libpng.patch [2]
- qt5base/5.8.0/0002-fix-VNC-platform-plugin-build-on-big-endian-machines.patch [3]
- qt5base/5.8.0/0003-QAtomic-pass-explicit-failure-mode-to-std-atomic-com.patch [4]
- qt5base/5.8.0/0003-eglfs-fix-x11-header-related-compile-failure.patch [5]
- qt5base/5.8.0/0004-examples-fix-compile-without-gui-module.patch [6]
- qt5webkit/0003-Exclude-backtrace-API-for-non-glibc-libraries.patch [7]

The qt5webkit patches no longer apply to both the LTS and latest
version, so they are moved to per-version directories.

[1] https://www.qt.io/qt5-9/
[2] https://code.qt.io/cgit/qt/qtbase.git/commit/?id=4dcfd90e4fd7d4c49138038dbbcbda8794a9fbff
[3] https://code.qt.io/cgit/qt/qtbase.git/commit/?id=6f64bfa654fb7e20bb75ec3b0544b81482babb44
[4] https://code.qt.io/cgit/qt/qtbase.git/commit/?id=5cc0de2e084cb887a75b076b82cf470ecdcd4dd3
[5] https://code.qt.io/cgit/qt/qtbase.git/commit/?id=e9a7739e77f79baeb5452189b6d17e63de5b341d
[6] https://code.qt.io/cgit/qt/qtbase.git/commit/?id=18d49808db46add078d9d4bcffaac5361d5c7269
[7] https://code.qt.io/cgit/qt/qtwebkit.git/commit/?id=548380af096f8277e460383c81a4ecdf2b77523f

Signed-off-by: Joshua Henderson <joshua.henderson@microchip.com>
Cc: Julien Corjon <corjon.j@ecagroup.com>
Cc: Brent Sink <brents_3@hotmail.com>
Cc: Naoki Matsumoto <n-matsumoto@melcoinc.co.jp>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>