Update FAQ section on large files (Bug#37818)

* doc/misc/efaq.texi (Problems with very large files): Extend section
and remove information about ancient versions of Emacs.

doc/misc/efaq.texi

@@ -2918,20 +2918,29 @@ type @kbd{C-h C-p} to read it.
 @end menu
 
 @node Problems with very large files
-@section Does Emacs have problems with files larger than 8 megabytes?
+@section Does Emacs have problems with large files?
 @cindex Very large files, opening
 @cindex Large files, opening
 @cindex Opening very large files
 @cindex Maximum file size
 @cindex Files, maximum size
 
-Old versions (i.e., anything before 19.29) of Emacs had problems editing
-files larger than 8 megabytes.  In versions 19.29 and later, the maximum
-buffer size is at least @math{2^{27}-1}, or 134,217,727 bytes, or 132 MBytes.
-The maximum buffer size on 32-bit machines increased to 256 MBytes in
-Emacs 22, and again to 512 MBytes in Emacs 23.2.
+Emacs has an inherent fixed limitation on the size of buffers.  This
+limit is stricter than the maximum size of objects supported by other
+programs on the same architecture.
 
-Emacs compiled on a 64-bit machine can handle much larger buffers.
+The maximum buffer size on 32-bit machines is 512 MBytes beginning
+with version 23.2.  If Emacs was built using the
+@code{--with-wide-int} flag, the maximum buffer size on 32-bit
+machines is 2 GB.
+
+Emacs compiled on a 64-bit machine can handle much larger buffers; up
+to @code{most-positive-fixnum} (2.3 exabytes).
+
+Due to things like decoding of multibyte characters, you can only
+visit files with a size that is roughly half the buffer size limit.
+When visiting compressed archives, the file size limit will be
+smaller than that due to decompression.
 
 @node ^M in the shell buffer
 @section How do I get rid of @samp{^M} or echoed commands in my shell buffer?