[Fontconfig] mmap-ed caches + patch

[Patrick Lam]

Lubos Lunak wrote:
>  However, when I tested the 2.3.90 release yesterday, I was originally 
> disappointed to see it performed noticeably worse than the last stable 
> version. Short version: Please apply the attached patch. Longer version: The 
> problem turned out to be directories that contain files that fontconfig 
> doesn't seem to use yet it analyses them (.pcf.gz files). If a directory 
> contains only .pcf.gz files and has no subdirectories, then the code that the 
> patch removes will not write a cache file, yet the return FcTrue means the 
> directory has been successfully cached. However if you look in 
> FcCacheReadDirs() you can see that if it can't use the cache file it will 
> call FcDirScanConfig(). So I suggest the attached patch which will write a 
> more or less empty cache file even in such directories.

Yes, I've applied your patch.  The current implementation of
FcDirCacheWrite does allow it to successfully write zero-length cache
files.  (In the past, it would have crashed, but I seem to have fixed
those cases.)

pat