regex man-page confusion

[Thomas Wolff]

(Sending this to cygwin-apps as I suspect it to be an installation or 
packaging issue...)

I observe a confusing discrepancy between Cygwin installations on two 
systems, all with cygwin 2.11.1:
On one system (both cygwin32 and cygwin64), /usr/share/man has 
man3/regex.3.gz and man3p/regcomp.3p,
both pages describe functions regcomp, regexec, regerror and regfree, 
but in different format (from man3, it says BSD manual).
On the other system, none of them exists, nor any other 
/usr/share/man/*/reg* (MANPATH not set). But `man regcomp` nonetheless 
displays a manpage, with those 4 functions and additionally wcs_regcomp 
and wcs_regexec.
Can anyone resolve this weirdness?
Thanks, Thomas