Enable hardware-acceleration in software (#2803)

This should not change the current behaviour, but toggles hardware
acceleration from the code rather than from the manifest.
Make hardware acceleration optional (#2803)
Disable hardware acceleration on some devices (#2803)

The HTC One X and the Samsung S3 mini have trouble rendering bold text
in hardware accelerated mode. On those devices, the default is to not
enable hardware acceleration.
Merge branch 'issue-2803' into upstream

Conflicts:
	main/res/xml/preferences.xml