Set local-lib to refer to the local import library

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.

See http://issue.cc/r3/2116 for details.

Author: BrianHawley

src/mezz/sys-base.r

@@ -129,6 +129,7 @@ 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
 
@@ -180,6 +181,7 @@ 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.r

@@ -120,7 +120,7 @@ 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.r file in" file]