If a header-only library requires linking a 3rd party library, the ..._LIBRARIES variable could not be used in depending projects, because it
contained NOTFOUND.

Automatically adding CMAKE_CXX_STANDARD to all projects is giving too much trouble because different CMAKE versions add different --std=gnu... flags which do not play well the the --std=c++... which we use.

This reverts commit ddb4d575.

This confused git massively

The pkg-config file is missing so we have to search for the library
manually

This is a work-around for libDOOCSapi linking against it but expecting
/export/doocs/lib to be in the linker search path (not using rpath)

May be reverted once/if doocs fixes this

FindDOOCS: extend PKG_CONFIG_PATH by directory set via DOOCS_DIR (if set) and the hardcoded default in /export/doocs/...

add two more ignores related to eclipse projects.

THis is necessary for newer Boost (1.71) which puts the exported targets
in Boost_LIBRARIES. If we export that verbatim it causes link issues on
projects using the config scripts from Make

This reverts commit e7294d81.

This does not exist on xenial yet

find_package is for use inside the *Config.cmake files

To add public dependencies to the generated config, use e.g.

list(APPEND ${PROJECT_NAME}_PUBLIC_DEPENDENCIES "Boost COMPONENTS system thread chrono")