MinGW build failure for GDB 8.2.90 with source-highlight

[Eli Zaretskii]

> Date: Thu, 07 Mar 2019 11:59:47 -0500
> From: Simon Marchi <simon.marchi@polymtl.ca>
> Cc: gdb-patches@sourceware.org
> 
> Since there are problems to fix with open on mingw (according to [1]), I 
> think it's fine that gnulib provides replacements.

For calls into the C runtime, sure.  But I don't think they can
replace the methods reflected to C++, because libstdc++ will call the
C runtime against which it was linked, at least on MS-Windows.

> Undefining the macros seems dangerous too, if you actually use the 
> "open" function from the C standard library on a system where it is 
> buggy, you want to end up with gnulib's fixed version...

There's no such call in source-cache.c, AFAICS.