Gerbil v0.18.2 Release Preparation

[vyzo]

Work that needs to complete in order to release Gerbil v0.18.2

• [x] Update Gambit v4.9.6 which was recently released: #1307
• [x] Finish and merge #1263
• [ ] Update documentation for typed gerbil and all associated changes (don't forget the demise of libgerbil.so): #1356
• [ ] Resolve #1242 / #1243
• [ ] #1308
• [ ] #1311
• [x] #1318
• [x] #1320

More stuff that has come up:

• [ ] #1352
• [ ] #1353
• [ ] #1354
• [ ] #1337
• [x] #1266 -- implement full signature injection for interface methods

And my pet peeves, on which i have flip flopped about a 100 times:

• [ ] union types
• [ ] auto procedure return type inference without the user needing to declare the type
• [ ] move the interpreter time compiler to gambit into the expander, so that we can reduce the weight of the runtime.

[vyzo]

So we have been discussing making this v0.19; there are so many changes, it is not just a patch release.