Add tests for shadowed functions in core Octave (bug #46849).

* test/load-path/refresh-load-path.tst: Add tests that check that warnings for
shadowed core functions are emitted.
* test/load-path/shadowed-builtin/quad.m,
test/load-path/shadowed-corelib/plot.m: Add new test files.
* test/load-path/module.mk: Add new files to build system.

Author: mmuetzel

test/load-path/module.mk

@@ -1,6 +1,8 @@
 load_path_TEST_FILES = \
     %reldir%/refresh-load-path.tst \
     %reldir%/in-load-path/load_path_fcn.m \
-    %reldir%/not-in-load-path/load_path_fcn.m
+    %reldir%/not-in-load-path/load_path_fcn.m \
+    %reldir%/shadowed-builtin/var.m \
+    %reldir%/shadowed-corelib/plot.m
 
 TEST_FILES += $(load_path_TEST_FILES)

test/load-path/refresh-load-path.tst

@@ -36,3 +36,21 @@
 %!   path (path_orig);
 %!   cd (pwd_orig);
 %! end_unwind_protect
+
+%!warning <shadows a built-in function>
+%! path_orig = path ();
+%! unwind_protect
+%!   addpath (fullfile (pwd (), "shadowed-builtin"));
+%! unwind_protect_cleanup
+%!   path (path_orig);
+%! end_unwind_protect
+
+## The following test only works after Octave has been installed and
+## __pathorig__ is non-empty.
+## %!warning <shadows a core library function>
+## %! path_orig = path ();
+## %! unwind_protect
+## %!   addpath (fullfile (pwd_orig, "shadowed-corelib"));
+## %! unwind_protect_cleanup
+## %!   path (path_orig);
+## %! end_unwind_protect

test/load-path/shadowed-builtin/quad.m

@@ -0,0 +1,3 @@
+## function which shadows a built-in function with the same name
+function var ()
+endfunction

test/load-path/shadowed-corelib/plot.m

@@ -0,0 +1,3 @@
+## function which shadows a function with the same name in Octave's core library
+function plot ()
+endfunction