Adds compilation unit/compunit to the glossary

It was missing so far, with compunit pointing to the definition of
several compilation units. Once again, @jnthn document is essential,
and definition sentence basically copypasted from there. Refs #502.

Author: JJ

doc/Language/glossary.pod6

@@ -456,22 +456,30 @@ X<|autopun>
 A self-referencing pun, e.g. "Are you ignorant or apathetic?" - "I don't
 know, and I don't care."
 
-=head2 backlog
 X<|backlog>
+=head2 backlog
 
 That part of a discussion on an L<#IRC> channel that you've missed.  If it is
 not or no longer available in your IRC client, you can go to sites such as
 L<http://colabti.org/irclogger/irclogger_logs/perl6> to see what has been logged
 for you.
 
-=head2 Bot
 X<|Bot>
+=head2 Bot
 
 A program that does automatic tasks on one or more L<#IRC> channels by
 acting like a regular user (as far as the IRC server is concerned) and
 performing some tasks that may involve answering to users requests.
 Examples are L<#camelia>, L<#dalek> and L<#yoleaux>.
 
+X<|compunit (glossary)>
+X<|compilation unit>
+=head2 Compilation unit or I<compunit>
+
+A compunit is L<a piece of Perl 6 code that is analyzed and compiled as a single unit|https://github.com/rakudo/rakudo/blob/master/docs/module_management.md>.
+Typically, this piece of code will be contained in a single file, but code
+inside an L<EVAL> is also considered a compunit.
+
 =head2 DWIM
 X<|DWIM>
 
@@ -717,7 +725,10 @@ and are subject to L<Multi-Dispatch|#Multi-Dispatch>.
 
 =head1 NFG
 
-Normal Form Grapheme is the way Perl 6 implements graphemes, using a normal form in which strings with the same graphemes can be easily compared in constant time. More on that on L<this article in 6guts|https://6guts.wordpress.com/2015/04/12/this-week-unicode-normalization-many-rts/> and an explanation of how NFG works in L<this IRC log|https://irclog.perlgeek.de/perl6/2018-04-29#i_16110340>.
+Normal Form Grapheme is the way Perl 6 implements graphemes, using a normal form
+in which strings with the same graphemes can be easily compared in constant
+time. More on that on L<this article in 6guts|https://6guts.wordpress.com/2015/04/12/this-week-unicode-normalization-many-rts/>
+and an explanation of how NFG works in L<this IRC log|https://irclog.perlgeek.de/perl6/2018-04-29#i_16110340>.
 
 =head1 Niecza
 X<|Niecza>
@@ -873,10 +884,10 @@ Repositories store not only files, but also history of changes and can be used
 by the developing or writing team for interaction through issues or comments to
 code.
 
-In Perl 6 context, however, a repository is a short name for I<compilation unit
-repository> and constitutes a system that locates and loads modules, managing
-their installation and precompilation. They are structured as linked lists,
-including chain of repositories ending in the default
+In Perl 6 context, however, a repository is also a short name for I<compilation
+unit repository> and constitutes a system that locates and loads modules,
+managing their installation and precompilation. They are structured as linked
+lists, including chain of repositories ending in the default
 C<Compunit::Repository::Installation>.
 
 X<|RHS>