doc: Correct `--enable-version-specific-runtime-libs' support information

The `--enable-version-specific-runtime-libs' configuration option is now
supported throughout all of our target library subdirectories, so update
installation documentation accordingly and also mention that the default
for the option is `yes' for libada and `no' for the remaining libraries.

	gcc/
	* doc/install.texi (Options specification): Remove the list of
	target library subdirectories supporting
	`--enable-version-specific-runtime-libs'.  Document defaults for
	the option.

From-SVN: r278871

gcc/ChangeLog

+2019-11-30  Maciej W. Rozycki  <macro@wdc.com>
+
+	* doc/install.texi (Options specification): Remove the list of
+	target library subdirectories supporting
+	`--enable-version-specific-runtime-libs'.  Document defaults for
+	the option.
+
 2019-11-29  Vladimir Makarov  <vmakarov@redhat.com>
 
 	PR rtl-optimization/92283

gcc/doc/install.texi

@@ -1559,8 +1559,8 @@ addition, @samp{libstdc++}'s include files will be installed into
 @file{@var{libdir}} unless you overruled it by using
 @option{--with-gxx-include-dir=@var{dirname}}.  Using this option is
 particularly useful if you intend to use several versions of GCC in
-parallel.  This is currently supported by @samp{libgfortran},
-@samp{libstdc++}, and @samp{libobjc}.
+parallel.  The default is @samp{yes} for @samp{libada}, and @samp{no} for
+the remaining libraries.
 
 @item @anchor{WithAixSoname}--with-aix-soname=@samp{aix}, @samp{svr4} or @samp{both}
 Traditional AIX shared library versioning (versioned @code{Shared Object}