Add missing doc index for imageutils and fnmatch

We added these two modules recently, but didn't include them in doc
index. This commit add them in doc index and add version information
about when they were added.

Change-Id: Ic3347f57a722187fc4bfe68fce6f08fba97af7fb

doc/source/index.rst

@@ -23,6 +23,8 @@ API Documentation
    api/excutils
    api/fileutils
    api/fixture
+   api/fnmatch
+   api/imageutils
    api/importutils
    api/netutils
    api/reflection

oslo_utils/fnmatch.py

@@ -15,6 +15,8 @@
 Standard library fnmatch in Python versions <= 2.7.9 has thread safe
 issue, this module is created for such case. see:
 https://bugs.python.org/issue23191
+
+.. versionadded:: 3.3
 """
 
 from __future__ import absolute_import

oslo_utils/imageutils.py

@@ -17,6 +17,8 @@
 
 """
 Helper methods to deal with images.
+
+.. versionadded:: 3.1
 """
 
 import re
@@ -26,6 +28,12 @@ from oslo_utils import strutils
 
 
 class QemuImgInfo(object):
+    """Parse Qemu image information from command `qemu-img info`'s output.
+
+    The instance of :class:`QemuImgInfo` has properties: `image`,
+    `backing_file`, `file_format`, `virtual_size`, `cluster_size`,
+    `disk_size`, `snapshots` and `encrypted`.
+    """
     BACKING_FILE_RE = re.compile((r"^(.*?)\s*\(actual\s+path\s*:"
                                   r"\s+(.*?)\)\s*$"), re.I)
     TOP_LEVEL_RE = re.compile(r"^([\w\d\s\_\-]+):(.*)$")