Compatibility with Solaris standard C library

[rdmark]

The Solaris standard C library defines a bgets symbol in libgen.h which conflicts with this library

https://docs.oracle.com/cd/E36784_01/html/E36877/bgets-3gen.html

This changeset introduces a build system check for this symbol and wraps a workaround in preprocessor macros

You can also force the workaround with -Dforce-bgets-workaround=true

[rdmark]

In the vendored version of bstring that we ship with netatalk, we have renamed the bgets symbol to bgetstream to solve the same problem, but I was thinking that we don't want to break the ABI in this library. What do you think about this approach for Solaris support?

Edit: And I should note here that the symbol naming conflict doesn't rear its ugly head when building bstring by itself, but you run into it when linking with an application like netatalk that pulls in more of the Solaris standard C library headers.

[msteinert]

I recall thinking it would have been nice if the entire API had a bstr_ prefix or similar. I agree it would be a shame to break backward compatibility.

How about a meson option to enable the name change? Enable it automatically if the setup script detects that symbol on Solaris?

[rdmark]

Sure, I guess it could be handy to have an override just in case: Updated the PR with option -Dforce-bgets-workaround=true