Add make fixincludes target.

All source files were already updated with IWYU in commit 7a9bc3d,
so no source file changes are needed.

src/.iwyu-overrides.imp

@@ -0,0 +1,12 @@
+[
+# Override for bugs at time of writing (8.22):
+{ symbol: [ "va_start", private, "<stdarg.h>", public ] },
+{ symbol: [ "va_arg", private, "<stdarg.h>", public ] },
+{ symbol: [ "va_end", private, "<stdarg.h>", public ] },
+{ symbol: [ "SIGIO", private, "<signal.h>", public ] },
+{ symbol: [ "SIGTSTP", private, "<signal.h>", public ] },
+{ symbol: [ "SIGPOLL", private, "<signal.h>", public ] },
+{ symbol: [ "SIGWINCH", private, "<signal.h>", public ] },
+{ symbol: [ "SIGCONT", private, "<signal.h>", public ] },
+{ symbol: [ "size_t", private, "<stdlib.h>", public ] },
+]

src/Makefile.am

@@ -1,3 +1,7 @@
+IWYU = iwyu
+IWYU_FLAGS = --error --mapping_file=.iwyu-overrides.imp
+IWYU_TRANSFORMED_FLAGS = $(patsubst %,-Xiwyu %,$(IWYU_FLAGS)) $(CFLAGS)
+
 EXTRA_DIST = sopwith.ico
 
 appdir = $(prefix)/share/applications
@@ -43,6 +47,11 @@ COMMON_SOURCES =                   \
         vid_vga.c                  \
         yocton.c     yocton.h
 
+fixincludes:
+	for d in *.c */*.c; do \
+		$(IWYU) $(IWYU_TRANSFORMED_FLAGS) 2>&1 $$d | fix_include; \
+	done
+
 if HAVE_WINDRES
 sopwith_SOURCES = $(COMMON_SOURCES) resource.rc
 else