[WIP] [travis] [appveyor] miscellaneous issues

[timotheecour]

major

• setup travis on windows, see https://github.com/nim-lang/Nim/issues/8640#issuecomment-429570179 [obsolete w azure-pipelines]
• [appveyor] queuing time is too slow (> 5 hours!) => should we buy more machines? #8640 [obsolete w azure-pipelines]
• [proposal] [CI] run whitelist of popular nimble packages as a part of non-blocking CI suite, to catch regressions early [proposal] run whitelist of popular nimble packages as a part of non-blocking CI suite, to catch regressions early #8638
• Aoptim: [RFC] skip CI runs (travis/AppVeyor) when AST doesn't change [RFC] skip CI runs (travis/AppVeyor) when AST doesn't change #8265
• PR (unattended): CI: Don't to run the tests if only the docs were updated (WIP) CI: Don't to run the tests if only the docs were updated (WIP) #6999
• [travis] flaky test: Failure: reOutputsDiffer in tests/parallel/tsysspawn.nim [WONTFIX] threadpool.sync buggy causing [travis] flaky test: Failure: reOutputsDiffer in tests/parallel/tsysspawn.nim #8226
• [CI] CI jobs shouldn't rerun automatically unless triggered via PR close/reopen or PR push to reduce resource consumption / queuing time [CI] CI jobs shouldn't rerun automatically unless triggered via PR close/reopen or PR push to reduce resource consumption / queuing time #8560
• [travis] fails with 0 work being done: "No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself." [WONTFIX] [travis] fails with 0 work being done: "No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself." #8698
• [travis] The job exceeded the maximum time limit for jobs, and has been terminated [TODO] [travis] The job exceeded the maximum time limit for jobs, and has been terminated #8707
• [tester] autotester should add OSX; eg using macincloud or macstadium [tester] autotester should add OSX; eg using macincloud or macstadium #8493
• [travis] [async] flaky test: tests/async/t7758.nim [travis] [async] flaky test: tests/async/t7758.nim #8756
• [appveyor] flaky test: Failure: reOutputsDiffer in tforstmt.nim echo not thread safe on windows, causing [appveyor] flaky test: Failure: reOutputsDiffer in tforstmt.nim #8511
• tfragment_alloc.nim (which allocates 4GB) often crashes appveyor tfragment_alloc.nim (which allocates 4GB) often makes appveyor fail with out of memory #8509

minor

• directed acyclic graph (DAG) dependencies cause a pkg to be installed twice, prompting a user prompt, causing travis to timeout Exports TXmlNode and the k TXmlNodeKind field. #511
• should we have defined(appveyor), defined(travis), defined(continousintegration) ? should we have defined(appveyor), defined(travis), defined(continousintegration) ? #8515

notes

WORKAROUND when a flaky test fails (from https://stackoverflow.com/questions/17606874/trigger-a-travis-ci-rebuild-without-pushing-a-commit): close PR and reopen PR

checkme

• "AppVeyor fails every single time with this export. Will investigate." from Exports dom.Style #8444 (comment)