Document two argument form of gdb.Value constructor

gdb/ChangeLog:

	* NEWS: Mention two argument form of gdb.Value constructor.

gdb/doc/ChangeLog:

	* python.texi (Values From Inferior): Document second form
	of Value.__init__.

gdb/ChangeLog

@@ -1,5 +1,6 @@
 2019-02-26  Kevin Buettner  <kevinb@redhat.com>
 
+	* NEWS: Mention two argument form of gdb.Value constructor.
 	* python/py-value.c (convert_buffer_and_type_to_value): New
 	function.
 	(valpy_new): Parse arguments via gdb_PyArg_ParseTupleAndKeywords.

gdb/NEWS

@@ -202,6 +202,9 @@ FreeBSD/riscv			riscv*-*-freebsd*
      gdb.SYMBOL_TYPES_DOMAIN are now deprecated.  These were never
      correct and did not work properly.
 
+  ** The gdb.Value type has a new constructor, which is used to construct a
+     gdb.Value from a Python buffer object and a gdb.Type.
+
 * Configure changes
 
 --enable-ubsan

gdb/doc/ChangeLog

@@ -1,3 +1,8 @@
+2019-02-26  Kevin Buettner  <kevinb@redhat.com>
+
+	* python.texi (Values From Inferior): Document second form
+	of Value.__init__.
+
 2019-02-23  Joel Brobecker  <brobecker@adacore.com>
 
 	* gdb.texinfo: Update copyright year ranges.

gdb/doc/python.texi

@@ -735,6 +735,14 @@ its result is used.
 @end table
 @end defun
 
+@defun Value.__init__ (@var{val}, @r{[}, type @r{]})
+This second form of the @code{gdb.Value} constructor returns a
+@code{gdb.Value} of type @var{type} where the value contents are taken
+from the Python buffer object specified by @var{val}.  The number of
+bytes in the Python buffer object must be greater than or equal to the
+size of @var{type}.
+@end defun
+
 @defun Value.cast (type)
 Return a new instance of @code{gdb.Value} that is the result of
 casting this instance to the type described by @var{type}, which must