scripts/: Add support for placeholders

Allow for specifying placeholders in shell scripts that are replaced
during build time. Predefine a "@PACKAGE_VERSION@" placeholder that is
replaced with the current version number. Also, rename all shell scripts
to ".sh.in".

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

scripts/Makefile.am

@@ -4,10 +4,16 @@ dist_bin_SCRIPTS = \
 	calcurse-upgrade
 
 EXTRA_DIST = \
-	calcurse-upgrade.sh
+	calcurse-upgrade.sh.in
 
 CLEANFILES = \
 	calcurse-upgrade
 
-calcurse-upgrade: calcurse-upgrade.sh
-	$(AM_V_GEN) $(INSTALL) $< $@
+edit = sed \
+	-e 's|@PACKAGE_VERSION[@]|$(PACKAGE_VERSION)|g'
+
+calcurse-upgrade: calcurse-upgrade.sh.in
+	$(AM_V_at)$(RM) "$@"
+	$(AM_V_GEN)$(edit) <"$(srcdir)/$<" >"$@"
+	$(AM_V_at)chmod +x "$@"
+	$(AM_V_at)chmod a-w "$@"