Code cleanup: Make parts of print_command_1 public

Code cleanup: Make parts of print_command_1 public

The later 'compile print' command should share its behavior with the existing
'print' command.  Make the needed existing parts of print_command_1 public.

gdb/ChangeLog
2015-05-16  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* printcmd.c (struct format_data): Move it to valprint.h.
	(print_command_parse_format, print_value): New functions from ...
	(print_command_1): ... here.  Call them.
	* valprint.h (struct format_data): Move it here from printcmd.c.
	(print_command_parse_format, print_value): New declarations.