Merge pull request #5 from boostorg/develop

Merge from develop
Merge branch 'develop'
Merge pull request #6 from boostorg/develop

rvalue ref overloads do not return by value
Merge branch 'develop'
typo
Merge pull request #10 from Siddhant/patch-1

typo in docs
Update 13_relational_operators.qbk

Missing word
Merge pull request #11 from OlafvdSpek/patch-1

Update 13_relational_operators.qbk