document bashs globstar setting #381

Job	Run time
linux (tiny, clang, native)	1m 40s
macos (tiny)	1m 25s
macos (normal)	10m 46s
windows (HUGE, msvc, no, no, x64, stable)	11m 1s
linux (tiny, gcc, native)	1m 52s
windows (HUGE, mingw, yes, yes, x86, stable, yes)	17m 29s
macos (huge)	14m 55s
linux (normal, clang, native)	1m 54s
windows (HUGE, msvc, no, yes, x86)	12m 45s
linux (normal, gcc, native)	1m 29s
windows (HUGE, mingw, yes, no, x64, yes)	13m 38s
linux (huge, clang, native)	1m 23s
windows (NORMAL, msvc, yes, no, x86)	11m 41s
linux (huge, gcc, native)	1m 28s
windows (NORMAL, mingw, no, yes, x64)	11m 42s
linux (tiny, clang, nogui)	1m 40s
windows (TINY, msvc, yes, yes, x64)	3m 7s
linux (tiny, gcc, nogui)	1m 25s
windows (TINY, mingw, no, no, x86)	4m 4s
linux (normal, gcc, i386, ./src/shadow)	2m 17s
linux (huge, gcc, uchar, testgui, true, dynamic)	2m 13s
linux (huge, clang, asan, 5.1)	1m 32s
linux (huge, gcc, unittests, true)	2m 32s
linux (normal, gcc, vimtags)	2m 9s
	2h 16m 7s

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