Keep snippet vars definitions in a single format across all snippets and documentation.

The format is:

# var-name: value

Previously snippets used a mixture of the following formatting:

#var-name: value
#var-name : value
# var-name: value
# var-name : value

snippets/cc-mode/once

@@ -1,4 +1,4 @@
-#name : #ifndef XXX; #define XXX; #endif
+# name: #ifndef XXX; #define XXX; #endif
 # key: once
 # --
 #ifndef ${1:_`(upcase (file-name-nondirectory (file-name-sans-extension (buffer-file-name))))`_H_}