DOCUMENTATION fixes for a few modules

cloud/amazon/ec2_vpc_dhcp_options.py

@@ -29,8 +29,7 @@ options:
   domain_name:
     description:
       - The domain name to set in the DHCP option sets
-    required:
+    required: false
-      - false
     default: ""
   dns_servers:
     description:

windows/win_regmerge.py

@@ -31,7 +31,7 @@ description:
     - Suitable for use with registry files created using M(win_template).
     - Windows registry files have a specific format and must be constructed correctly with carriage return and line feed line endings otherwise they will not be merged.  
     - Exported registry files often start with a Byte Order Mark which must be removed if the file is to templated using M(win_template).
-    - Registry file format is described here: https://support.microsoft.com/en-us/kb/310516
+    - Registry file format is described at U(https://support.microsoft.com/en-us/kb/310516)
     - See also M(win_template), M(win_regedit)
 options:
   path:

windows/win_timezone.py

@@ -31,7 +31,7 @@ description:
 options:
   timezone:
     description:
-      - Timezone to set to.  Example: Central Standard Time
+      - Timezone to set to.  Example Central Standard Time
     required: true
     default: null
     aliases: []