[make help] mention INITCPIO switch (#137)

This commit is an expansion to :
87b8163

Since a new `make` parameter has been introduced, it should be mentioned
in the output of the `help` target.

Also, the table is being expanded by a new column describing the type of
data that each parameter may be assigned, like paths or boolean values.

Makefile

@@ -52,11 +52,12 @@ help:
 	@echo "           uninstall"
 	@echo "           help"
 	@echo
-	@echo "  parameters | description                    | defaults"
-	@echo "  -----------+--------------------------------+----------------------------"
-	@echo "  DESTDIR    | install destination            | <unset>"
-	@echo "  PREFIX     | system tree prefix             | '/usr'"
-	@echo "  SHARE_DIR  | shared data location           | '\$$(DESTDIR)\$$(PREFIX)/share'"
-	@echo "  LIB_DIR    | system libraries location      | '\$$(DESTDIR)\$$(PREFIX)/lib'"
-	@echo "  PKGNAME    | name of the ditributed package | 'grub-btrfs'"
+	@echo "  parameter | type | description                    | defaults"
+	@echo "  ----------+------+--------------------------------+----------------------------"
+	@echo "  DESTDIR   | path | install destination            | <unset>"
+	@echo "  PREFIX    | path | system tree prefix             | '/usr'"
+	@echo "  SHARE_DIR | path | shared data location           | '\$$(DESTDIR)\$$(PREFIX)/share'"
+	@echo "  LIB_DIR   | path | system libraries location      | '\$$(DESTDIR)\$$(PREFIX)/lib'"
+	@echo "  PKGNAME   | name | name of the ditributed package | 'grub-btrfs'"
+	@echo "  INITCPIO  | bool | include mkinitcpio hook        | false"
 	@echo