introduce $(SUDO) to make install with administrative privileges customizable

defaults.mk: define SUDO to map to sudo, add comment to define
	blank if administrative privileges are not needed (already root on
	Linux or Administrator on Windows)

	targets.mk: use newly defined $(SUDO) uinstead of plain sudo,
	replaces some braces with parentheses

default.mk

@@ -76,6 +76,10 @@ SED	= sed
 # CP	= cp -p	# try this if there is no install
 CP	= install -p
 
+# How to obtain administrative privileges
+# SUDO	= 	# leave blank if you don't need this
+SUDO	= sudo
+
 # Name of the program to install info files
 # INSTALL_INFO = ginstall-info # Debian: avoid harmless warning message
 INSTALL_INFO = install-info

targets.mk

@@ -44,12 +44,12 @@ test-dirty::
 	$(BTEST)
 
 up2:	update
-	sudo ${MAKE} install
+	$(SUDO) $(MAKE) install
 
 update:
 	git remote update
 	git pull
-	${MAKE} all
+	$(MAKE) all
 
 install:	$(INSTSUB)