revert to without with_gsl

CMakeLists.txt

@@ -133,6 +133,7 @@ ENDIF(NOT WIN32 AND NOT ANDROID)
 # required
 FIND_PACKAGE(Proj)
 FIND_PACKAGE(Expat)    # GPS importer plugin
+FIND_PACKAGE(GSL)      # Georeferencer
 FIND_PACKAGE(GEOS)
 FIND_PACKAGE(GDAL)
 FIND_PACKAGE(Qwt REQUIRED)
@@ -148,11 +149,6 @@ IF (NOT WITH_INTERNAL_SPATIALITE)
 ENDIF (NOT WITH_INTERNAL_SPATIALITE)
 
 # optional
-SET (WITH_GSL TRUE CACHE BOOL "Determines whether to load GSL (and thus the georeferencer plugin)")
-IF (WITH_GSL)
-  FIND_PACKAGE(GSL)      # Georeferencer
-ENDIF (WITH_GSL)
-
 IF (WITH_POSTGRESQL)
   FIND_PACKAGE(Postgres) # PostgreSQL provider, SPIT plugin
 ENDIF (WITH_POSTGRESQL)