Add RGBASM -Winclude-shadow warning (#2180)

contrib/bash_compl/_rgbasm.bash

@@ -185,6 +185,7 @@ _rgbasm_completions() {
 				empty-macro-arg
 				empty-strrpl
 				export-undefined
+				include-shadow
 				large-constant
 				macro-shift
 				nested-comment

contrib/zsh_compl/_rgbasm

@@ -17,6 +17,7 @@ _rgbasm_warnings() {
 		'empty-macro-arg:Warn on empty macro arg'
 		'empty-strrpl:Warn on calling STRRPL with empty pattern'
 		'export-undefined:Warn on EXPORT of an undefined symbol'
+		'include-shadow:Warn on multiple INCLUDE/INCBIN file candidates'
 		'large-constant:Warn on constants too large for a signed 32-bit int'
 		'macro-shift:Warn when shifting macro args part their limits'
 		'nested-comment:Warn on "/*" inside block comments'