earlier build_history_base: timing properties in log are introduced here;

--- a/.hgtags	Tue Oct 04 15:42:08 2016 +0200
+++ b/.hgtags	Tue Oct 04 18:09:23 2016 +0200
@@ -25,7 +25,7 @@
 6d736d983d5cfec4a6c6fba174db2cd93493a96b Isabelle2011
 76fef3e570043b84a32716b5633085d2fb215525 Isabelle2011-1
 21c42b095c841d1a7508c143d6b6e98d95dbfa69 Isabelle2012
-22630327408b4c4412761f738ee5b3ff9e25dcc4 build_history_base
+20126dd9772c973118879a6878acfd9e6c66f1e7 build_history_base
 d90218288d517942cfbc80a6b2654ecb22735e5c Isabelle2013
 9c1f2136532626c7cb5fae14a2aeac53be3aeb67 Isabelle2013-1
 4dd08fe126bad63aa05741d55fb3e86a2dbfc795 Isabelle2013-2