v8.4: Fixing a bug in the presence of let-in in inductive arity.
v8.4: Fixing a (new) part of bug #2729.

This commit fixes ill-typedness of the vm in #2729 when reconstructing
a "match" in an inductive type whose constructors have let-ins.

(backport from trunk)
v8.4: Fixing typo absorption (bug #3751).

(backport from trunk)
v8.4: Supporting Greek and Coptic (U0370) as first letter of coqdoc identifiers.

(backport from trunk)
v8.4: Fixing what really looks like a bug in the initial
implementation of coqdoc links for modules (#3756).

(backport from trunk)
v8.4: Fixing an evar leak in pattern-matching compilation (#3758).
Updating CHANGES.