BOOST_REQUIRE fails on Solaris due to hyphens in variable

[scantor]

I've had to patch around an issue using the boost.m4 file on Solaris. The sed command to extract the Boost version during the requirement check breaks and ends up with an empty version due to the use of hyphens in the macro.

I've found this patch works across platforms that I've tested by switching back to underscores:

http://git.shibboleth.net/view/?p=cpp-xmltooling.git;a=commitdiff;h=ad7702632e1a01c074f6ec15d2c0a937582be78c

Forgot to file this a few years ago and re-encountered it recently.