[1.6] string: fix max_size() return value

[1.6] Add missing include to v.hpp.

Needed by std::forward_as_tuple.

[1.6] cmake: require c++11 for cow check

[1.6] Bump pmdk to 1.6 in Docker images

C++ version was incorrectly computed by cmake to c++98 which resulted in compilation error on ubuntu 16.04

Introduce options to enable array/vector/string

Merge back changes from stable-1.5

Adjust TRAVIS_COMMIT_RANGE variable to contain only commits from a PR.

to contain only commits from a PR.

Ref: travis-ci/travis-ci/issues/4596

Limit job configurations run on travis.

[1.5] cmake: check if dot tool is installed

fix doxygen invalid \ref command

which is required by doxygen to generate graphs

fix clang compilation error

[1.5] fix typo

clang 7.0.0 triggers -Wself-assign-overloaded in case of explicit self assignment
whilst we handle this in our implementation

All words in the documentation that correspond to a documented
class and contain at least one non-lower case character will
automatically be replaced by a link to the page containing the
documentation of the class.

Merge back changes from stable-1.5

Add changelog for 1.6

Fix crash when previous transaction failed to start

string: cast null-terminator to proper type

... because of already taken lock.

Merge back changes from stable-1.5

test: add string tests for self assignment

to avoid Wsign-conversion.