_BOOST_FIND_LIBS doesn't honor 64bit libs

[jelmd]

_BOOST_FIND_LIBS fails to find 64bit libs since it doesn't check the amd64|x86_64 sub dirs of */lib/

if defined(__amd64) || defined(__x86_64)

env: boost 1.59 (Solaris 11.3, gcc 4.8.2)