[PATCH v2 0/4] Define gdb.Value(val, type) constructor

[Kevin Buettner <kevinb@redhat.com>]

This four part patch series defines a two argument constructor for
gdb.Value.

gdb.Value currently has a one argument constructor.  It takes a python
value, figures out some potentially suitable gdb type and then
constructs a gdb value of that type.

The two argument version that I'm introducing is useful for
constructing a gdb value of a specified type from a buffer of bytes. 
It takes the form gdb.Value (val, type).  VAL is a python buffer object,
i.e. an object from which bytes may be read using python's buffer
protocol.  TYPE is a gdb type perhaps obtained by calling
gdb.lookup_type().

Changes between the original series and this v2 series are as follows:

Patch #1: No changes.

Patch #2:

  Fix wording of comment noted by Simon.
  
  Change PyExc_RuntimeError to PyExc_TypeError for "type argument must
  be a gdb.Type" error.  I found this while adding the additional test
  that Simon suggested.

Patch #3:

  Add test which invokes gdb.Value where second argument is not
  a gdb.Type.  (Suggested by Simon.)

Patch #4:

  Add NEWS entry.  (Requested by Eli.)

  Made other python.texi changes requested by Eli.  

  Added missing "@end defun".