SDK 2.2.0 Release

Lock picotool version to 2.1.0 for backwards-compatibility

Lock picotool version on master to 2.1.1 (#2401)The master SDK branch (and the SDK release tags eg 2.1.1) should point to specific picotool tags, to ensure you get a compatible picotool (note this is beyond the 2.1.1 tag in master, so will just fix this for users who check out the HEAD of master)

SDK 2.1.1 Release

SDK 2.1.0 release

SDK 2.0.0 release

revert changes to when -nostartfiles is specified in link for 1.5.1 a……s it can cause link errors with C++; see#1368

release SDK 1.5.0

SDK 1.4.0 release

SDK 1.3.1 release