DGD 1.5, 1.6, 1.7

[dworkin]

• 1.5
  The focus was originally on JIT compiler support, which then shifted to being the bridge between 1.6 and versions before 1.5, when I realized how much the bytecode VM had to change to accommodate JIT compilation. The recently released 1.5.20 is the last one in the series.
• 1.6
  Focus on JIT compiler support. Will soon give way to...
• 1.7
  Initial focus on documentation.