patch 8.1.2082: some files have a weird name to fit in 8.3 characters

Problem:    Some files have a weird name to fit in 8.3 characters.
Solution:   Use a nicer names.
diff --git a/src/Make_morph.mak b/src/Make_morph.mak
index 9c070c8..f0d9cf8 100644
--- a/src/Make_morph.mak
+++ b/src/Make_morph.mak
@@ -81,7 +81,7 @@
 	option.c						\
 	optionstr.c						\
 	os_amiga.c						\
-	popupmnu.c						\
+	popupmenu.c						\
 	profiler.c						\
 	quickfix.c						\
 	regexp.c						\