OE-lite/core 6.3.0

This release contains a lot of internal improvements, some fixes, and a couple of minor new features.

Finally, a change in USE flag handling is introduced. It should be a semantic no-op, but please read the comments about it in PR #190 anyway, as it is a preparation to a bigger change that will come later on, which we would like to see people preparing for already now.

New features:

• Add --dryrun option for simple measurement of time spent on everything but building (PR #175).
• Add kernel_dts_vendor USE flag to kernel class (PR #193).

Improvements / cleanups:

• Reduced usage of sqlite (PR #148).
• Memory use reduction (PR #172).
• Various optimizations (PR #173, #177, #185, #195).
• Improvements to profiling and debug (PR #183, #184).
• Use wget command instead of urlgrabber module, avoiding problems with pycurl in Ubuntu, Debian and others (PR #178).
• Improved hash computation (PR #192).
• Prepare for saner USE flag handling (PR #190).

Fixes:

• Fix handling of s6rc bundles with '-' in name (PR #179).
• Avoid harmless but noisy error messages on Ubuntu (PR #170).
• Fix error handling on bad elf type in packageqa (PR #187).
• Fix handling of broken symlinks in do_package (PR #188).
• Fix problem with stdout/stderr buffering (PR #182).

Thanks to all who contributed to this release:

• Rasmus Villemoes (61 commits)
• Sean Nyekjaer (3 commits)
• Kim Højgaard-Hansen (2 commits)
• Esben Haabendal (1 commit)

With this release, master branch is now open for 7.0.0 pull requests.
In case further 6.x releases are needed, maintenance branches for that will be created.