[wip] remove all submodules
Squashed 'deps/picohttpparser/' content from commit 3dedc7d

git-subtree-dir: deps/picohttpparser
git-subtree-split: 3dedc7dc82b7fec1170a0cb382b03d2cd39291c5
Merge commit '2d1c19c3eb4e65e9af19f3c00744012c6abe56d8' as 'deps/picohttpparser'
Squashed 'deps/picotest/' content from commit d088dc1

git-subtree-dir: deps/picotest
git-subtree-split: d088dc13a78338f440443eea043994e0bcea3dfc
Merge commit 'a290fa2c86ba515c8c35ce8a4ade6af38cca5391' as 'deps/picotest'
Squashed 'deps/yoml/' content from commit d30e2fd

git-subtree-dir: deps/yoml
git-subtree-split: d30e2fd22febeccb85718d2775802c175b89b0f1
Merge commit '121193977bd361c831d994e98d68352675457de0' as 'deps/yoml'
Squashed 'deps/klib/' content from commit f28c067

git-subtree-dir: deps/klib
git-subtree-split: f28c067d3ef59ae650cc79326c833ccde69ecbcc
Merge commit '815ee90e860ef64e369f4a20c980db92f0dbe343' as 'deps/klib'
Merge branch 'kazuho/subtree-ize' (see also https://github.com/kazuho/picojson/issues/61#issuecomment-67118769)