HPX continuous integration build configurations

This is an overview of the configurations used to test test HPX. It may not always be up-to-date. CircleCI, Travis CI, and pycicle are run for every pull request. buildbot is run only for master.

Service	Builder name	OS	Build type	Compiler	C++ standard	Boost	hwloc	allocator	CUDA	networking	APEX
CircleCI	build-and-test	Linux (Ubuntu)	Debug	clang 8.0	auto	1.68	1.11	system	no	yes	no
Travis CI		Windows	Debug	MSVC 19	auto	1.70	?	system	no	yes	no
Travis CI		macOS	Debug	clang 9.1	auto	1.71	2.1.0	system	no	yes	no
pycicle, Piz Daint	gcc-oldest	Linux (SLES)	Debug	gcc 5.5	14	1.61	1.11.5	system	no	yes	no
pycicle, Piz Daint	gcc-newest	Linux (SLES)	Release	gcc 9.1	17	1.71	2.0.4	system	no	no	no
pycicle, Piz Daint	clang-oldest	Linux (SLES)	Debug	clang 5.0 (libc++)	14	1.61	1.11.11	system	no	yes	no
pycicle, Piz Daint	clang-newest	Linux (SLES)	Release	clang 9.0 (libc++)	17	1.71	2.1.0	system	no	yes	no
pycicle, Piz Daint	gcc-cuda	Linux (SLES)	Debug	gcc 8.3	14	1.70	2.0.3	jemalloc 5.1.0	10.1	yes	no
pycicle, Piz Daint	clang-cuda	Linux (SLES)	Debug	CCE (clang 9)	17	1.69	2.0.3	system	10.1	yes	no
pycicle, Piz Daint	icc	Linux (SLES)	Debug	icc 19	auto	1.70	2.0.3	system	no	yes	no
pycicle, Piz Daint	clang-apex	Linux (SLES)	Debug	clang 8.0 (libc++)	17	1.69	2.0.3	system	no	yes	yes
buildbot, Rostam	various	CentOS	various	various	auto	various	various	various	various	yes	no