rename mach.icns to thunderbird.icns for clarity

mail/app/Makefile.in

@@ -181,7 +181,7 @@ ifeq ($(OS_ARCH),WINNT)
 	cp $(srcdir)/thunderbird.ico   $(DIST)/branding/app.ico
 endif
 ifneq (,$(filter mac cocoa,$(MOZ_WIDGET_TOOLKIT)))
-	cp $(srcdir)/macbuild/mach.icns  $(DIST)/branding/mach.icns
+	cp $(srcdir)/macbuild/thunderbird.icns  $(DIST)/branding/thunderbird.icns
 endif
 ifneq (,$(filter gtk gtk2,$(MOZ_WIDGET_TOOLKIT)))
 	cp $(srcdir)/mozicon16.xpm $(DIST)/branding/mozicon16.xpm
@@ -242,7 +242,7 @@ libs:: $(PROGRAM)
 	rsync -a $(DIST)/bin/ $(DIST)/$(APP_NAME).app/Contents/MacOS
 	rm -f $(DIST)/$(APP_NAME).app/Contents/MacOS/$(PROGRAM)
 	rsync -aL $(PROGRAM) $(DIST)/$(APP_NAME).app/Contents/MacOS
-	cp -RL $(DIST)/branding/mach.icns $(DIST)/$(APP_NAME).app/Contents/Resources/mach.icns
+	cp -RL $(DIST)/branding/thunderbird.icns $(DIST)/$(APP_NAME).app/Contents/Resources/thunderbird.icns
 	echo -n APPLMOZM > $(DIST)/$(APP_NAME).app/Contents/PkgInfo
 #       remove CVS dirs from packaged app
 	find $(DIST)/$(APP_NAME).app -type d -name "CVS" -prune -exec rm -rf {} \;