bison: new external at 2.7.1

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
flex: new external at 2.5.37

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
doxygen: new external at 1.8.4

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
doxygen: fix compilation on Darwin platform

Disable Objective-C via -DOS_OBJECT_USE_OBJC=0 macro. Needed since
OS X 10.8.

Signed-off-by: David Abdurachmanov <davidlt@cern.ch>
Merge pull request #137 from davidlt/IB/CMSSW_7_0_X/stable

[CMSSW_7_0_X] Bison 2.7.1; Flex 2.5.37; Doxygen 1.8.4