Fix gcc 6 warnings about invoking placement new on a buffer of insufficient size - #9

According to gcc, no official release of gcc6 has occurred yet. So I cannot see how I can test this against gcc6 until a release of gcc6 has been created and is available for an OS I run. I can test for gcc-5.3 and below as well as clang, VC++ etc but I would not be able to determine if this fixes an issue in gcc6.

According to https://gcc.gnu.org/ gcc 6.1 has been released on 2016-04-15. On boost develop test page there are Flast-FreeBSD10-gcc-6.0.0~gnu++11 and trippels-powerpc64le-gcc-6.0 testers, which use gcc 6 and show the warnings e.g. here: http://www.boost.org/development/tests/develop/output/trippels-powerpc64le-gcc-6-0-log-gcc-6-0-1-warnings.html#filt_matches_spirit_classic.

I now realize that trippels shows version 6.0.1, which is not the final gcc 6 version (6.1). So I guess I didn't see the warnings on the final gcc 6 yet, but I'm fairly sure they will be present there.

I just followed the gcc 6 link on https://gcc.gnu.org/, and it says (at https://gcc.gnu.org/gcc-6/) "As of this time no releases of GCC 6 have yet been made." My expectation is that release is imminent.

Fedora 24 is the only Linux distro which I have found and which I run that will have gcc6 upon its release as the default version of gcc. Fedora24 will be available in June. I have not found any information when mingw-64 on Windows will have a gcc6 version. I understand that it might be possible to build gcc6 now from source but I am loth to try this myself. I will be glad to test your fix for gcc6 when I can do it with a released version.

Hi,

Has this change been reviewed already ? I will apply it locally on my local copy of Boost but I would feel better if this pull request was accepted and merged into the official repo ;)

Cheers,
Romain

There are currently multiple gcc 6 testers in the test matrix. Could someone apply this PR so that it at least receives regular testing?