regexp: wrong match with 'ic' and comparing multi-byte with single by… #707

Job	Run time
macos (tiny, macos-12)	1m 7s
linux (tiny, clang, native)	3m 18s
windows (HUGE, msvc, no, no, x64, stable)	6m 5s
linux (tiny, gcc, native)	2m 50s
windows (HUGE, mingw, yes, yes, x86, stable, yes)	11m 39s
linux (normal, clang, native)	5m 48s
windows (HUGE, msvc, no, yes, x86)	9m 33s
macos (tiny, macos-14)	43s
linux (normal, gcc, native)	6m 4s
windows (HUGE, mingw, yes, no, x64, yes)	10m 29s
macos (normal, macos-12)	6m 23s
linux (huge, clang, native)	9m 48s
windows (NORMAL, msvc, yes, no, x86)	7m 2s
macos (normal, macos-14)	4m 27s
linux (huge, gcc, native)	11m 14s
windows (NORMAL, mingw, no, yes, x64)	9m 24s
macos (huge, macos-12)	14m 35s
linux (tiny, clang, nogui)	2m 20s
windows (TINY, msvc, yes, yes, x64)	2m 11s
macos (huge, macos-14)	14m 7s
linux (tiny, gcc, nogui)	2m 30s
windows (TINY, mingw, no, no, x86)	2m 56s
linux (normal, gcc, i386, ./src/shadow)	6m 51s
linux (huge, gcc, uchar, testgui, true, dynamic)	10m 12s
linux (huge, clang, asan, 5.1)	17m 25s
linux (huge, gcc, unittests, true)	2m 38s
linux (normal, gcc, vimtags)	2m 25s
	3h 4m 4s

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