installer: made kohaversion.pl source for package version number

Version now taken from kohaversion.pl instead of
C4/Context.pm, aligning installer with the rest
of Koha's internal version checks.

Makefile.PL

@@ -418,7 +418,7 @@ if ($config{'INSTALL_MODE'} ne "dev") {
 WriteMakefile(
     NAME => 'koha',
     #VERSION => strftime('2.9.%Y%m%d%H',gmtime),
-    VERSION_FROM => 'C4/Context.pm',
+    VERSION_FROM => 'kohaversion.pl',
     ABSTRACT => 'Award-winning integrated library system (ILS) and Web OPAC',
     AUTHOR => 'Koha Developers <koha-devel@nongnu.org>',
     NO_META => 1,

kohaversion.pl

@@ -7,8 +7,14 @@
 #        used by developers when the database changes. updatedatabase take care of the changes itself
 #        and is automatically called by Auth.pm when needed.
 
+use strict;
+
 sub kohaversion {
-    return "3.00.00.035";
+    our $VERSION = "3.00.00.35";
+    # version needs to be set this way
+    # so that it can be picked up by Makefile.PL
+    # during install
+    return $VERSION;
 }
 
 1;