The BSDs and sysconf()

Hi all, 

I’ve moved past signal handling for now and have reached file mapping for my book on the guts of 
LibreOffice - https://www.gitbook.com/book/chrissherlock1/inside-libreoffice/details 
<https://www.gitbook.com/book/chrissherlock1/inside-libreoffice/details>

As I’ve been reading through how we handle file mapping, I’ve noticed we do something a bit unusual 
for finding the page size on BSD systems. From what I can see, OpenBSD, NetBSD, FreeBSD, OS X and 
DragonflyBSD all supports sysconf() now. However, we have some special cased code in 
sal/osl/unx/file.cxx that is used by the file mapping API when it gets the pagesize of the system. 
Currently it is special casing out the BSDs to use getpagesize(), and everything else that is POSIX 
compliant uses sysconf(_SC_PAGESIZE). 

However, I checked out the latest man pages for all the BSDs, and they all seem to support 
sysconf(_SC_PAGESIZE). Is there any reason we are checking the platform and using getpagesize() for 
the BSDs now?

I’ve submitted a gerrit change in case there is no good reason:

https://gerrit.libreoffice.org/#/c/39120/ <https://gerrit.libreoffice.org/#/c/39120/>

If anyone would like to review it, would be great. 

Chris