Update Boost detection to CMake's CONFIG scheme

Author: heplesser

cmake/ProcessOptions.cmake

@@ -294,11 +294,9 @@ function( NEST_PROCESS_WITH_GSL )
       set( GSL_ROOT "${with-gsl}" )
     endif ()
 
-    find_package( GSL )
+    find_package( GSL 1.11 )
 
-    # only allow GSL 1.11 and later
-    if ( GSL_FOUND AND ( "${GSL_VERSION}" VERSION_GREATER "1.11"
-        OR "${GSL_VERSION}" VERSION_EQUAL "1.11" ))
+    if ( GSL_FOUND )
       set( HAVE_GSL ON PARENT_SCOPE )
 
       # export found variables to parent scope
@@ -550,7 +548,8 @@ function( NEST_PROCESS_WITH_BOOST )
     set(Boost_USE_RELEASE_LIBS ON) # only find release libs
     # Needs Boost version >=1.62.0 to use Boost sorting, JUNIT logging
     # Require Boost version >=1.69.0 due to change in Boost sort
-    find_package( Boost 1.69.0 )
+    # Require Boost version >=1.70.0 due to change in package finding
+    find_package( Boost 1.70 CONFIG )
     if ( Boost_FOUND )
       # export found variables to parent scope
       set( HAVE_BOOST ON PARENT_SCOPE )