Set library path when running Python tests

Copied from libxml2.

Should fix #75.

python/tests/Makefile.am

@@ -9,5 +9,8 @@
 dist_example_DATA = test.xml test.xsl pyxsltproc.py $(TESTSPY)
 
 tests: $(TESTSPY)
-	@(PYTHONPATH="`pwd`/..:`pwd`/../.libs:$(srcdir)/.."; \
+	@(export PYTHONPATH="..:../.libs:$(srcdir)/..:$$PYTHONPATH"; \
+	  export LD_LIBRARY_PATH="$(top_builddir)/libxslt/.libs:$(top_builddir)/libexslt/.libs:$$LD_LIBRARY_PATH"; \
+	  export DYLD_LIBRARY_PATH="$(top_builddir)/libxslt/.libs:$(top_builddir)/libexslt/.libs:$$DYLD_LIBRARY_PATH"; \
+	  export PATH="$(top_builddir)/libxslt/.libs:$(top_builddir)/libexslt/.libs:$$PATH" ; \
 	  if test "x$(LIBXML_SRC)" != "x" ; then \
@@ -13,3 +16,6 @@
 	  if test "x$(LIBXML_SRC)" != "x" ; then \
-            PYTHONPATH="$$PYTHONPATH:$(LIBXML_SRC)/python:$(LIBXML_SRC)/python/.libs"; \
+            PYTHONPATH="$(LIBXML_SRC)/python:$(LIBXML_SRC)/python/.libs:$$PYTHONPATH"; \
+	    LD_LIBRARY_PATH="$(LIBXML_SRC)/.libs:$$LD_LIBRARY_PATH"; \
+	    DYLD_LIBRARY_PATH="$(LIBXML_SRC)/.libs:$$DYLD_LIBRARY_PATH"; \
+	    PATH="$(LIBXML_SRC)/.libs:$$PATH" ; \
           fi; \
@@ -15,5 +21,4 @@
           fi; \
-	  export PYTHONPATH; \
 	  for test in $(TESTSPY) ; do \
 	    echo "-- $$test" ; \
 	    (cd $(srcdir) && $(PYTHON) $$test ) || exit 1; \