[boost] [epochs] Boost conditional dependency map

As part of the epoch proposal, I've written a small toolchain to generate a so-called Boost conditional dependency map: https://github.com/joaquintides/boostcdmap/ Such a map gives, for each Boost module and each epoch Boost03, ... , Boost20, the dependencies of the module under the given epoch (which may vary across epochs). The actual map for Boost 1.73 is provided at: https://github.com/joaquintides/boostcdmap/blob/master/boostcdmap.1.73.0.jso... The conditional dependency map is a key asset for the automation of epoch assignment; I'll elaborate on this point in the upcoming days. As always, comments welcome. Best regards, Joaquín M López Muñoz