boost: Use wildcard in version for bbappend

Makes it apply to any version of boost from here on.

Signed-off-by: Khem Raj <raj.khem@gmail.com>

recipes-support/boost/boost_%.bbappend

+PACKAGECONFIG_append = " python"

recipes-support/boost/boost_1.54.0.bbappend

-PACKAGECONFIG ?= "python"