Add extended attribute support (Linux) #384

Job	Run time
macos (tiny)	1m 19s
linux (tiny, clang, native)	2m 15s
macos (normal)	8m 14s
windows (HUGE, msvc, no, no, x64, stable)	9m 46s
linux (tiny, gcc, native)	2m 48s
macos (huge)	19m 38s
windows (HUGE, mingw, yes, yes, x86, stable, yes)	18m 41s
linux (normal, clang, native)	6m 8s
windows (HUGE, msvc, no, yes, x86)	14m 47s
linux (normal, gcc, native)	6m 46s
windows (HUGE, mingw, yes, no, x64, yes)	14m 45s
linux (huge, clang, native)	9m 36s
windows (NORMAL, msvc, yes, no, x86)	11m 26s
linux (huge, gcc, native)	9m 50s
windows (NORMAL, mingw, no, yes, x64)	16m 52s
linux (tiny, clang, nogui)	1m 49s
windows (TINY, msvc, yes, yes, x64)	4m 34s
linux (tiny, gcc, nogui)	1m 50s
windows (TINY, mingw, no, no, x86)	4m 4s
linux (normal, gcc, i386, ./src/shadow)	9m 34s
linux (huge, gcc, uchar, testgui, true, dynamic)	8m 38s
linux (huge, clang, asan, 5.1)	27m 27s
linux (huge, gcc, unittests, true)	2m 43s
linux (normal, gcc, vimtags)	1m 35s
	3h 35m 5s

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