enable python module build in subdir

[Michael Tokarev]

Unbound Makefile has two small issues preventing
building python modules in a non-source directory
(eg in a subdir).

First, swig fails to find <libunbound/unbound.h>
which is not in build dir but in source dir.

Next, libunbound/python/unbound.py is now being
generated file, generated in the build dir, not
in source dir.

This patch fixes them.

Signed-off-by: Michael Tokarev <mjt at tls.msk.ru>

diff --git a/Makefile.in b/Makefile.in
index 55125a44..f04db624 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -59,3 +59,3 @@ CC=@CC@
 CPPFLAGS=-I. @CPPFLAGS@
-PYTHON_CPPFLAGS=-I. @PYTHON_CPPFLAGS@
+PYTHON_CPPFLAGS=-I$(srcdir) @PYTHON_CPPFLAGS@
 CFLAGS=-DSRCDIR=$(srcdir) @CFLAGS@
@@ -558,3 +558,3 @@ pyunbound-install:
 	$(INSTALL) -m 755 -d $(DESTDIR)$(PYTHON_SITE_PKG)
-	$(INSTALL) -c -m 644 $(srcdir)/libunbound/python/unbound.py $(DESTDIR)$(PYTHON_SITE_PKG)/unbound.py
+	$(INSTALL) -c -m 644 libunbound/python/unbound.py $(DESTDIR)$(PYTHON_SITE_PKG)/unbound.py
 	$(LIBTOOL) --mode=install cp _unbound.la $(DESTDIR)$(PYTHON_SITE_PKG)