Cleanup some of the PACKAGE_XXX variables and rely in the ones given by the project() command

cmake/generateConfigFile.cmake

@@ -10,9 +10,9 @@ set(EXV_ENABLE_WEBREADY  ${EXIV2_ENABLE_WEBREADY})
 set(EXV_HAVE_LENSDATA    ${EXIV2_ENABLE_LENSDATA})
 set(EXV_HAVE_PRINTUCS2   ${EXIV2_ENABLE_PRINTUCS2})
 
-set(EXV_PACKAGE          ${PACKAGE})
+set(EXV_PACKAGE_NAME     ${PROJECT_NAME})
 set(EXV_PACKAGE_VERSION  ${PROJECT_VERSION})
-set(EXV_PACKAGE_STRING   ${PACKAGE_STRING})
+set(EXV_PACKAGE_STRING   "${PROJECT_NAME} ${PROJECT_VERSION}")
 if (${EXIV2_ENABLE_XMP} OR ${EXIV2_ENABLE_EXTERNAL_XMP})
     set(EXV_HAVE_XMP_TOOLKIT ON)
 else()