Hello,
dupstring_wlen (i.e. with-len) is ready to use, so this patch is just
4 changes dupstring(s) -> dupstring_wlen(s, l). Each of those
dupstrings has a nice strlen() invocation already there in lex.c, a
few lines above.

Callgrind doesn't report any real change in number of instructions of
strlen() call and a test that repeatedly invokes (z) flag on a 32-line
buffer 150 times reports 24 ms for both unoptimized and optimized
version.

However performance test of F-Sy-Highlighting reports rather stable 40
ms gain – out of ~3000 ms, so not much.

In general simplicity of this patch made me send it.

-- 
Sebastian Gniazdowski
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