Merge branch 'fix_for_issue_21' into 'master'

fixes #21: add OPAL include directories at the beginning

See merge request !4

ippl/src/CMakeLists.txt

@@ -145,7 +145,7 @@ SET (MAKE_DEF
 
 
 INCLUDE_DIRECTORIES (
-    ${CMAKE_CURRENT_SOURCE_DIR}
+    BEFORE ${CMAKE_CURRENT_SOURCE_DIR}
     )
 
 IF (ENABLE_DKS)

src/CMakeLists.txt

@@ -73,7 +73,7 @@ add_subdirectory (ValueDefinitions)
 
 add_sources (opal.cpp)
 
-include_directories (
+include_directories ( BEFORE
     ${OPAL_SRC_DIR}
     ${CLASSIC_SRC_DIR}
     ${IPPL_INCLUDE_DIR}