add def_value_str and use it in qemu_opts_print.

qemu_opts_print has no user now, so can re-write the function safely.

qemu_opts_print will be used while using "qemu-img create", it will
produce the same output as previous code.

The behavior of this function has changed:

1. Print every possible option, whether a value has been set or not.
2. Option descriptors may provide a default value.
3. Print to stdout instead of stderr.

Previously the behavior was to print every option that has been set.
Options that have not been set would be skipped.

v7->v8:
1) print "elements => accept any params" while opts_accepts_any() ==
true.
2) since def_print_str is the default value if an option isn't set,
so rename it to def_value_str.

Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
Create four opts list related functions

This patch will create 4 functions, count_opts_list, append_opts_list,
free_opts_list and print_opts_list, they will used in following commits.

v6->v7):
1) Fix typo.

v5->v6):
1) allocate enough space in append_opts_list function.

Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
Use QemuOpts support in block layer

This patch will use QemuOpts related functions in block layer, add
a member bdrv_create_options to BlockDriver struct, it will return
a QemuOptsList pointer, which includes the image format's create
options.

And create options's primary consumer is block creating related functions,
so modify them together.

v8->v9)
1) add qemu_ prefix to gluster_create_opts.
2) fix bug: bdrv_gluster_unix and bdrv_gluster_rdma should also be
   converted.

v7->v8)
1) rebase to upstream source tree.
2) add gluster.c, raw-win32.c, and rbd.c.

v6->v7:
1) use osdep.h:stringify(), not redefining new macro.
2) preserve TODO comment.
3) fix typo. BLOCK_OPT_ENCRYPT->BLOCK_OPT_STATIC.
4) initialize disk_type even when opts is NULL.

v5->v6:
1) judge if opts == NULL in block layer create functions.
2) use bdrv_create_file(filename, NULL) in qcow_create and cow_create funtion.
3) made more readable while using qemu_opt_get_number.

Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>

Conflicts:

	block/raw-posix.c
remove QEMUOptionParameter related functions and struct

Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>