Problem: send_multipart fails on old gcc versions

[gummif]

Solution: remove template type checks if there is only partial C++11 support

[gummif]

Should fix https://github.com/zeromq/cppzmq/issues/365

[coveralls]

Pull Request Test Coverage Report for Build 346

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 86.483%

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Totals
Change from base Build 335:	0.0%
Covered Lines:	691
Relevant Lines:	799

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💛 - Coveralls

[sigiesec]

Ok, thanks! As long as there are no other overloads that might cause ambiguity, this is probably ok.