FEAT: Set local-lib to refer to the local import library

resolves: Oldes/Rebol-wishes#13

Instead of having the local import library object have no referent
once the module is running except the words you bound from it, set
the word local-lib in the module context to refer to it. This will
let the developer control overrides, just like lib does globally.

Also set local-lib to system/contexts/user in the script context.
Even though there is nothing for scripts like the object target
of local imports in modules, presetting the word will prevent it
from being a problem when modules unnecessarily export it, and it
will serve as a shortcut way to refer to the context, like lib.

(cherry picked from commit 69667f0)

Author: Oldes

src/mezz/sys-base.reb

@@ -132,6 +132,7 @@ make-module*: func [
 	if find spec/options 'extension [
 		append obj 'lib-base ; specific runtime values MUST BE FIRST
 	]
+	append obj 'local-lib ; local import library for the module
 
 	unless spec/type [spec/type: 'module] ; in case not set earlier
 
@@ -183,6 +184,7 @@ make-module*: func [
 	]
 
 	bind body obj
+	obj/local-lib: any [mixins make object! 0] ; always set, always overrides
 	if block? hidden [protect/hide/words hidden]
 	obj: to module! reduce [spec obj]
 	do body

src/mezz/sys-start.reb

@@ -131,7 +131,7 @@ start: func [
 
 	;-- Make the user's global context:
 	tmp: make object! 320
-	append tmp reduce ['system :system]
+	append tmp reduce ['system :system 'local-lib :tmp]
 	system/contexts/user: tmp
 
 	;boot-print ["Checking for user.reb file in" file]