enforce current BH

Author: kevinushey

DESCRIPTION

@@ -23,7 +23,7 @@ Suggests:
     RUnit,
     knitr,
     rmarkdown
-LinkingTo: BH
+LinkingTo: BH (>= 1.60.0-1)
 SystemRequirements: GNU make, Windows: cmd.exe and cscript.exe, Solaris: g++ is required
 License: GPL-2
 URL: http://rcppcore.github.io/RcppParallel, https://github.com/RcppCore/RcppParallel