Added XML tests for the C-part to make sure not only library but also include files are found

cmake/tests/test_XML.c

+#include <libxml/parser.h>
+#include <libxml/tree.h>
+#include <libxml/xmlschemas.h>
+#include <libxml/xpath.h>
+#include <libxml/xpathInternals.h>
+
+int main()
+{
+  return 0;
+}
+

cmake/tests/test_XML.cmake

@@ -17,9 +17,23 @@ try_compile(FLEUR_USE_XML ${CMAKE_BINARY_DIR} ${CMAKE_SOURCE_DIR}/cmake/tests/te
        endif()
 endif()       
 
-message("XML Library found:${FLEUR_USE_XML}")
+message("XML Library found for linking:${FLEUR_USE_XML}")
+
+if (FLEUR_USE_XML)
+   try_compile(FLEUR_USE_XML ${CMAKE_BINARY_DIR} ${CMAKE_SOURCE_DIR}/cmake/tests/test_XML.c
+   LINK_LIBRARIES ${FLEUR_LIBRARIES})
+   if (NOT FLEUR_USE_XML)
+      find_package(LibXml2)
+      set(CMAKE_C_FLAGS "-I${LIBXML2_INCLUDE_DIR}")
+      try_compile(FLEUR_USE_XML ${CMAKE_BINARY_DIR} ${CMAKE_SOURCE_DIR}/cmake/tests/test_XML.c
+      LINK_LIBRARIES ${FLEUR_LIBRARIES})
+   endif()
+endif()
+
+message("XML Library found for C:${FLEUR_USE_XML}")
+
 
 if (FLEUR_USE_XML)
    set(FLEUR_DEFINITIONS ${FLEUR_DEFINITIONS} "CPP_XML") 
    set(FLEUR_MPI_DEFINITIONS ${FLEUR_MPI_DEFINITIONS} "CPP_XML")
-endif()
\ No newline at end of file
+endif()