use small_vector in more places #750

Job	Run time
msvc-x64, Release, Shared=ON	3m 10s
msvc-x64, Release, Shared=OFF	2m 58s
clang-x64, Release, Shared=ON	4m 16s
clang-x64, Release, Shared=OFF	4m 17s
msvc-x64, RelWithDebInfo, Shared=ON	3m 43s
msvc-x64, RelWithDebInfo, Shared=OFF	3m 33s
clang-x64, RelWithDebInfo, Shared=ON	6m 1s
clang-x64, RelWithDebInfo, Shared=OFF	4m 16s
msvc-Win32, RelWithDebInfo, Shared=ON	3m 55s
msvc-Win32, RelWithDebInfo, Shared=OFF	3m 42s
clang-Win32, RelWithDebInfo, Shared=ON	5m 54s
clang-Win32, RelWithDebInfo, Shared=OFF	5m 48s
	51m 33s

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