docs: Use short first paragraphs for module index.

LDoc uses the first paragraph of each modules doccomment as in the
front page index.  Put back the one liners we used to have.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>

Author: gvvaughan

lib/std/prototype/container.lua

@@ -1,4 +1,6 @@
 --[[--
+ Container Prototype.
+
  This module supplies the root prototype object from which every other
  object is descended.  There are no classes as such, rather new objects
  are created by cloning an existing object, and then changing or adding

lib/std/prototype/object.lua

@@ -1,4 +1,6 @@
 --[[--
+ Object Prototype.
+
  This module provides a specialization of the @{prototype.container.prototype}
  with the addition of object methods.  In addition to the functionality
  described here, object prototypes also have all the methods and

lib/std/prototype/set.lua

@@ -1,4 +1,6 @@
 --[[--
+ Set Prototype.
+
  This module returns a table of set operators, as well as the prototype
  for a Set container object.
 

lib/std/prototype/strbuf.lua

@@ -1,4 +1,6 @@
 --[[--
+ StrBuf Prototype.
+
  Buffers are mutable by default, but being based on objects, they can
  also be used in a functional style:
 

lib/std/prototype/trie.lua

@@ -1,4 +1,6 @@
 --[[--
+ Trie Prototype.
+
  This module returns a table of trie operators, as well as the prototype
  for a Trie container object.