add def_value_str in QemuOptDesc struct and rewrite qemu_opts_print

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

qemu_opts_print is used while using "qemu-img create", it
produces 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.

v13->v14:
1) fix memory leak.
2) make opt_set do not accpet null value argument.

v12->v13
1) re-write commit message.

v11->v12
1) make def_value_str become the real default value string in opt_set
function.

v10->v11:
1) print all values that have actually been assigned while accept-any
cases.

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.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
avoid duplication of default value in QemuOpts

This patch moves the default value entirely to QemuOptDesc.

When getting the value of an option that hasn't been set, and
QemuOptDesc has a default value, return that.  Else, behave as
before.

Example: qemu_opt_get_number(opts, "foo", 42)

   If "foo" has been set in opts, return its value.

   Else, if opt's QemuOptDesc has a default value for "foo", return
   that.

   Else, return 42.

   Note that the last argument is useless when QemuOptDesc has a
   default value.  Ugly.  If it bothers us, we could assert.

Example: qemu_opt_get(opts, "bar")

   If "bar" has been set in opts, return its value.

   Else, if opt's QemuOptDesc has a default value for "bar", return
   that.

   Else, return NULL.

Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

v13->v14:
1) change code style.
2) assert errors.

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

This patch creates 4 functions, count_opts_list, qemu_opts_append,
qemu_opts_free and qemu_opts_print_help, they are used in following
commits.

v16->v17:
1) fix indentation.
2) fix typo.

v15->v16:
1) discard double-initialization.
2) use pointer directly, not g_strdup.

v12->v13:
1) simply assert that neither argument has merge_lists set.
2) drop superfluous paranthesesis around p == first.

v11->v12:
1) renmae functions.
2) fix loop styles and code styles.
3) qemu_opts_apend will not return NULL now.
4) merge_lists value is from arguments in qemu_opts_append.

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>
Create some QemuOpts functons

These functions will be used in next commit.

qemu_opt_get_(*)_del functions are used to make sure we
have the same behaviors as before: in block layer, after
parsing a parameter value, parameter list will delete it
to avoid parsing it twice.

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

v17->v18:
1) return "char *" instead of "const char*"

v13->v14:
1) rewrite commit message.
2) use def_value_str in qemu_opt_get_FOO_del() and qemu_opt_get_del().
3) delete redundant qemu_opt_del(opt).
Use QemuOpts support in block layer

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

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

v13->v14:
1) add block/ssh.c support.
2) fix memory leak after using qemu_opt_get_del.

v12->v13:
1) split into 2 patches. one for block, one for QemuOpts funcitons.
2) fix leaking cco->opts.
3) other small fix.

v11->v12:
1) create functions, such as qemu_opt_get_del and qemu_opt_replace_set.
These functions works like origin code.
2) use QEMU_OPT_SIZE, not QEMU_OPT_NUMBER.
3) in bdrv_create, if opts is NULL, will create an empty one, so can
discard if(opts) code safely.

v10->v11:
1) qed.h move QED_DEFAULT_CLUSTER_SIZE from enum to macro, or
qemu_opts_print produce un-expanded cluster_size.
2) In qcow2.c and qcow.c, bdrv_create_file(filename, NULL), NULL ->
opts,
or while using protocol, there will be an error.

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>
query-command-line-options outputs def_value_str

QMP command query-command-line-options shows details information of
parameters, since added def_value_str, also output it in the QMP
command.

v16->v17:
1) add "Since 1.6" tag.
2) rename def_str_value to "default".

Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
remove QEMUOptionParameter related functions and struct

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>