Add $(VARNISHSRC)/lib/libvsc to include path

VSC_main.h has moved

Spotted by: jw

src/Makefile.am

 AUTOMAKE_OPTIONS = subdir-objects
 
-AM_CFLAGS = $(VARNISHAPI_CFLAGS) -I$(VARNISHSRC)/include \
-	-I$(VARNISHSRC)/bin/varnishd -I$(VARNISHSRC)/lib/libvgz \
+AM_CFLAGS = \
+	$(VARNISHAPI_CFLAGS) \
+	-I$(VARNISHSRC)/include \
+	-I$(VARNISHSRC)/bin/varnishd \
+	-I$(VARNISHSRC)/lib/libvgz \
+	-I$(VARNISHSRC)/lib/libvsc \
 	-Wall -Werror -Wextra -std=c99
 AM_LDFLAGS = $(VARNISHAPI_LIBS) $(VMOD_LDFLAGS) -ldl