syntax: lua: condense some regexes, tweak comments, reorder things

Also remove some redundant backslashes and parentheses.

syntax/lua.nanorc

 ## Syntax highlighting for Lua.
 #
-## Author:  Matthew Wild <mwild1 (at) gmail.com>
+## Original author:  Matthew Wild <mwild1 (at) gmail.com>
 ## License: GPL 3 or later
-## Version: 2011-05-05
 
 syntax "lua" "\.lua$"
 magic "Lua script"
@@ -20,46 +19,39 @@ color brightblue "\<(do|end|while|repeat|until|if|elseif|then|else|for|in|functi
 color brightyellow "\<(_G|_VERSION|assert|collectgarbage|dofile|error|getfenv|getmetatable|ipairs|load|loadfile|module|next|pairs|pcall|print|rawequal|rawget|rawlen|rawset|require|select|setfenv|setmetatable|tonumber|tostring|type|unpack|xpcall)\s*\("
 
 # Standard library
-color brightyellow "\<io\.(close|flush|input|lines|open|output|popen|read|tmpfile|type|write|stdin|stdout|stderr)\>"
-color brightyellow "\<math\.(abs|acos|asin|atan2|atan|ceil|cosh|cos|deg|exp|floor|fmod|frexp|huge|ldexp|log10|log)\>"
-color brightyellow "\<math\.(max|maxinteger|min|mininteger|mod|modf|pi|pow|rad|random|randomseed|sinh|sin|sqrt|tan)\>"
-color brightyellow "\<math\.(tointeger|type|ult)\>"
+color brightyellow "\<coroutine\.(create|isyieldable|resume|running|status|wrap|yield)\>"
+color brightyellow "\<debug\.(debug|(get|set)(fenv|hook|info|local|metatable|(up|user)value)|getregistry|traceback|upvalue(id|join))\>"
+color brightyellow "\<io\.(close|flush|input|lines|output|p?open|read|tmpfile|type|write|std(in|out|err))\>"
+color brightyellow "\<math\.(abs|acos|asin|atan2?|ceil|cosh?|deg|exp|floor|fmod|frexp|huge|ldexp|log10|log)\>"
+color brightyellow "\<math\.((max|min)(integer)?|modf?|pi|pow|rad|random(seed)?|sinh?|sqrt|tan|tointeger|type|ult)\>"
 color brightyellow "\<os\.(clock|date|difftime|execute|exit|getenv|remove|rename|setlocale|time|tmpname)\>"
 color brightyellow "\<package\.(config|cpath|loaded|loadlib|path|preload|searchers|searchpath|seeall)\>"
 color brightyellow "\<string\.(byte|char|dump|find|format|gmatch|gsub|len|lower|match|pack|packsize|rep|reverse|sub|unpack|upper)\>"
 color brightyellow "\<table\.(concat|insert|maxn|move|pack|remove|sort|unpack)\>"
-color brightyellow "\<coroutine\.(create|isyieldable|resume|running|status|wrap|yield)\>"
-color brightyellow "\<debug\.(debug|getfenv|gethook|getinfo|getlocal|getmetatable|getregistry|getupvalue|getuservalue)\>"
-color brightyellow "\<debug\.(setfenv|sethook|setlocal|setmetatable|setupvalue|setuservalue|traceback|upvalueid|upvaluejoin)\>"
 color brightyellow "\<utf8\.(char|charpattern|codepoint|codes|len|offset)\>"
 
 # File handle methods
 color brightyellow ":(close|flush|lines|read|seek|setvbuf|write)\>"
 
-# false, nil, true
-color brightmagenta "\<(false|nil|true)\>"
-
 # External files
 color brightgreen "\<(dofile|require)\>"
 
-# Numbers
+# Special words
+color brightmagenta "\<(false|nil|true)\>"
+
+# Decimal and hexadecimal numbers
 color red "\<[0-9]+(\.[0-9]*)?([Ee][+-]?[0-9]+)?\>"
+icolor red "\<0x[0-9a-f]+(\.[0-9a-f]*)?(p[+-]?[0-9]+)?\>"
 
-# Symbols
-color brightmagenta "(\(|\)|\[|\]|\{|\})"
+# Brackets
+color brightmagenta "\(|\)|\[|\]|\{|\}"
 
 # Shebang
-color brightcyan   "^#!.*"
-
-# Simple comments
-color green        "\-\-.*$"
+color brightcyan "^#!.*"
 
-# Multiline comments
-color green         start="\-\-\[\[" end="\]\]"
+# Simple comments and multiline comments
+color green "--.*"
+color green start="--\[\[" end="\]\]"
 
 # Strings
 color red ""(\\.|[^"\])*"|'(\\.|[^'\])*'"
-##color red         start="\[\[" end="\]\]"
-
-# Hex literals
-icolor red "\<0x[0-9a-f]+(\.[0-9a-f]*)?(p[+-]?[0-9]+)?\>"