K 10
svn:author
V 8
tcberner
K 8
svn:date
V 27
2018-12-29T23:07:16.960604Z
K 7
svn:log
V 520
deskutils/kmail: include optional.h from boost to fix build on recent CURRENT

On FreeBSD Current optional is no longer in experimental/optional.
Further, switching  to c++17 to use it, would require changes to
databases/akonadi to no longer use auto_ptr.

As this all would be a hassle, follow what upstream has done for a
similar problem with akonadi on Windows [1]: Import a 3rdparty optional.h
and use that.

[1] https://github.com/KDE/akonadi/commit/482315f4cbc79d3725738fa1e62c8e0ce053bdea

PR:             234022

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