hardfork: block 192239 switched to smaller retarget window/limits.

 - 540 blocks retarget window
 - 1.25 target update limits

 - checkpoint added.
 - version bumped to 0.8.0.2
Merge branch 'dev-0.1.3' into release-0.1.3
Merge branch 'release-0.1.3'
v0.8.0.2 stable build
build script version update
Merge branch 'master' into release-0.1.3
release branch & unstable flag.
Merge branch 'release-0.1.3' into dev-0.1.3