Add RGBASM -Winclude-shadow warning (#2180)

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'