Rework the way the makefile controls which modules should be excluded.

Instead of commenting out some blocks of code, now the list of modules
to exclude is controlled by the DEVEL variable: setting it to 1 means
that we are on a development version (default); when preparing for a
package release, this should be set to 0.

Makefile

@@ -1,23 +1,28 @@
 ## PACKAGE MAKEFILE
 RSCRIPT = "$(R_HOME)/bin/Rscript"
 
+## set to 1 when on a development version, or to 0 when preparing a release
+DEVEL := 1
+
+## modules to exclude: it should not be necessary to touch these, they are
+## controlled by the DEVEL variable set before
+EXCLUDE_MODULES := \
+	'module_check_ReverseDependencies', \
+	'module_write_codemetar' \
+	$(NULL)
+ifeq ($(DEVEL), 1)
+  EXCLUDE_MODULES += ,\
+	'module_add_RLumTeam', \
+	'module_add_HowToCite', \
+	'module_write_BibTeX', \
+	'module_write_FunctionList', \
+	'module_write_PDF_manual' \
+	$(NULL)
+endif
+
 all:
 	${RSCRIPT} -e "RLumBuild::build_package(\
 		exclude = c(\
-		'module_check_ReverseDependencies',\
-		'module_write_codemetar',\
-		'module_add_RLumTeam',\
-		'module_add_HowToCite',\
-		'module_write_BibTeX',\
-		'module_write_FunctionList',\
-		'module_write_PDF_manual'),\
+		$(EXCLUDE_MODULES) ),\
 		as_cran = TRUE,\
 		write_Rbuildignore = TRUE)";
-
-#all:
-#	${RSCRIPT} -e "RLumBuild::build_package(\
-#		exclude = c(\
-#		'module_check_ReverseDependencies',\
-#		'module_write_codemetar'),\
-#		as_cran = TRUE,\
-#		write_Rbuildignore = TRUE)";