- clarified constants and constant expressions
- clarified type of array composite literals (fixed vs open arrays)
- clarified type of map composite literals (need to use '&' to get
  a map pointer)
- added proposal for "if-else" (TBD)
- added TODO w/ respect to "x, ok = <-ch" (and for arrays)

R=r
DELTA=51  (35 added, 0 deleted, 16 changed)
OCL=15573
CL=15575