Move all lua related files to lua/ subfolder

Also remove the lexers sub directory from the Lua search path.
As a result we attempt to open fewer files during startup:

 $ strace -e open -o log ./vis +q config.h && wc -l log

In order to avoid having to modifiy all lexers which `require('lexer')`
we instead place a symlink in the top level directory.

 $ ./configure --disable-lua
 $ rm -rf lua

Should result in a source tree with most lua specifc functionality
removed.

1 files changed, 60 insertions, 0 deletions

diff --git a/lua/lexers/haskell.lua b/lua/lexers/haskell.lua
new file mode 100644
index 0000000..de247e1
--- /dev/null
+++ b/lua/lexers/haskell.lua
@@ -0,0 +1,60 @@
+-- Copyright 2006-2016 Mitchell mitchell.att.foicica.com. See LICENSE.
+-- Haskell LPeg lexer.
+-- Modified by Alex Suraci.
+
+local l = require('lexer')
+local token, word_match = l.token, l.word_match
+local P, R, S = lpeg.P, lpeg.R, lpeg.S
+
+local M = {_NAME = 'haskell'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Comments.
+local line_comment = '--' * l.nonnewline_esc^0
+local block_comment = '{-' * (l.any - '-}')^0 * P('-}')^-1
+local comment = token(l.COMMENT, line_comment + block_comment)
+
+-- Strings.
+local string = token(l.STRING, l.delimited_range('"'))
+
+-- Chars.
+local char = token(l.STRING, l.delimited_range("'", true))
+
+-- Numbers.
+local number = token(l.NUMBER, l.float + l.integer)
+
+-- Keywords.
+local keyword = token(l.KEYWORD, word_match{
+  'case', 'class', 'data', 'default', 'deriving', 'do', 'else', 'if', 'import',
+  'in', 'infix', 'infixl', 'infixr', 'instance', 'let', 'module', 'newtype',
+  'of', 'then', 'type', 'where', '_', 'as', 'qualified', 'hiding'
+})
+
+-- Identifiers.
+local word = (l.alnum + S("._'#"))^0
+local identifier = token(l.IDENTIFIER, (l.alpha + '_') * word)
+
+-- Operators.
+local op = l.punct - S('()[]{}')
+local operator = token(l.OPERATOR, op)
+
+-- Types & type constructors.
+local constructor = token(l.TYPE, (l.upper * word) + (P(":") * (op^1 - P(":"))))
+
+M._rules = {
+  {'whitespace', ws},
+  {'keyword', keyword},
+  {'type', constructor},
+  {'identifier', identifier},
+  {'string', string},
+  {'char', char},
+  {'comment', comment},
+  {'number', number},
+  {'operator', operator},
+}
+
+M._FOLDBYINDENTATION = true
+
+return M