Expose current 'print' settings to Python

PR python/17291 asks for access to the current print options.  While I
think this need is largely satisfied by the existence of
Value.format_string, it seemed to me that a bit more could be done.

First, while Value.format_string uses the user's settings, it does not
react to temporary settings such as "print/x".  This patch changes
this.

Second, there is no good way to examine the current settings (in
particular the temporary ones in effect for just a single "print").
This patch adds this as well.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=17291

gdb/python/python.c

@@ -2560,6 +2560,10 @@ the returned string is 'ADDRESS <SYMBOL+OFFSET>' without the quotes." },
     "current_language () -> string\n\
 Return the name of the currently selected language." },
 
+  { "print_options", gdbpy_print_options, METH_NOARGS,
+    "print_options () -> dict\n\
+Return the current print options." },
+
   {NULL, NULL, 0, NULL}
 };