Document "target:" sysroot changes

This commit documents the newly added "target:" sysroot feature.

gdb/ChangeLog:

	* NEWS: Announce the new default sysroot of "target:".

gdb/doc/ChangeLog:

	* gdb.texinfo (set sysroot): Document "target:".

gdb/ChangeLog

@@ -1,3 +1,7 @@
+2015-04-02  Gary Benson <gbenson@redhat.com>
+
+	* NEWS: Announce the new default sysroot of "target:".
+
 2015-04-02  Gary Benson <gbenson@redhat.com>
 
 	* main.c (captured_main): Set gdb_sysroot to "target:"

gdb/NEWS

@@ -24,6 +24,13 @@
   present in the debug info.  This typically includes the compiler version
   and may include things like its command line arguments.
 
+* Directory names supplied to the "set sysroot" commands may be
+  prefixed with "target:" to tell GDB to access shared libraries from
+  the target system, be it local or remote.  This replaces the prefix
+  "remote:".  The default sysroot has been changed from "" to
+  "target:".  "remote:" is automatically converted to "target:" for
+  backward compatibility.
+
 * Python Scripting
 
   ** gdb.Objfile objects have a new attribute "username",

gdb/doc/ChangeLog

@@ -1,3 +1,7 @@
+2015-04-02  Gary Benson <gbenson@redhat.com>
+
+	* gdb.texinfo (set sysroot): Document "target:".
+
 2015-04-01  Sasha Smundak  <asmundak@google.com>
 
 	* doc/python.texi (Writing a Frame Unwinder in Python): Add

gdb/doc/gdb.texinfo

@@ -17854,15 +17854,20 @@ libraries, they need to be laid out in the same way that they are on
 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
 under @var{path}.
 
-If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will 
+If @var{path} starts with the sequence @file{target:} and the target
-retrieve the target libraries from the remote system.  This is only
+system is remote then @value{GDBN} will retrieve the target binaries
-supported when using a remote target that supports the @code{remote get}
+from the remote system.  This is only supported when using a remote
-command (@pxref{File Transfer,,Sending files to a remote system}).
+target that supports the @code{remote get} command (@pxref{File
-The part of @var{path} following the initial @file{remote:}
+Transfer,,Sending files to a remote system}).  The part of @var{path}
-(if present) is used as system root prefix on the remote file system.
+following the initial @file{target:} (if present) is used as system
-@footnote{If you want to specify a local system root using a directory
+root prefix on the remote file system.  If @var{path} starts with the
-that happens to be named @file{remote:}, you need to use some equivalent
+sequence @file{remote:} this is converted to the sequence
-variant of the name like @file{./remote:}.}
+@file{target:} by @code{set sysroot}@footnote{Historically the
+functionality to retrieve binaries from the remote system was
+provided by prefixing @var{path} with @file{remote:}}.  If you want
+to specify a local system root using a directory that happens to be
+named @file{target:} or @file{remote:}, you need to use some
+equivalent variant of the name like @file{./target:}.
 
 For targets with an MS-DOS based filesystem, such as MS-Windows and
 SymbianOS, @value{GDBN} tries prefixing a few variants of the target