Allow more ways to write booleans in YAML

See http://yaml.org/type/bool.html and http://yaml.org/spec/1.2/spec.html#id2805071

runtime/syntax/yaml.yaml

@@ -6,8 +6,7 @@ detect:
 
 rules:
     - type: "(^| )!!(binary|bool|float|int|map|null|omap|seq|set|str) "
-    - constant:  "\\b(YES|yes|Y|y|ON|on|NO|no|N|n|OFF|off)\\b"
-    - constant: "\\b(true|false)\\b"
+    - constant:  "\\b(YES|yes|Y|y|ON|on|TRUE|True|true|NO|no|N|n|OFF|off|FALSE|False|false)\\b"
     - statement: "(:[[:space:]]|\\[|\\]|:[[:space:]]+[|>]|^[[:space:]]*- )"
     - identifier: "[[:space:]][\\*&][A-Za-z0-9]+"
     - type: "[-.\\w]+:"