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, 66 insertions, 0 deletions

diff --git a/lua/lexers/io_lang.lua b/lua/lexers/io_lang.lua
new file mode 100644
index 0000000..0d8b483
--- /dev/null
+++ b/lua/lexers/io_lang.lua
@@ -0,0 +1,66 @@
+-- Copyright 2006-2016 Mitchell mitchell.att.foicica.com. See LICENSE.
+-- Io LPeg lexer.
+
+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 = 'io_lang'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Comments.
+local line_comment = (P('#') + '//') * l.nonnewline^0
+local block_comment = '/*' * (l.any - '*/')^0 * P('*/')^-1
+local comment = token(l.COMMENT, line_comment + block_comment)
+
+-- Strings.
+local sq_str = l.delimited_range("'")
+local dq_str = l.delimited_range('"')
+local tq_str = '"""' * (l.any - '"""')^0 * P('"""')^-1
+local string = token(l.STRING, tq_str + sq_str + dq_str)
+
+-- Numbers.
+local number = token(l.NUMBER, l.float + l.integer)
+
+-- Keywords.
+local keyword = token(l.KEYWORD, word_match{
+  'block', 'method', 'while', 'foreach', 'if', 'else', 'do', 'super', 'self',
+  'clone', 'proto', 'setSlot', 'hasSlot', 'type', 'write', 'print', 'forward'
+})
+
+-- Types.
+local type = token(l.TYPE, word_match{
+  'Block', 'Buffer', 'CFunction', 'Date', 'Duration', 'File', 'Future', 'List',
+  'LinkedList', 'Map', 'Nop', 'Message', 'Nil', 'Number', 'Object', 'String',
+  'WeakLink'
+})
+
+-- Identifiers.
+local identifier = token(l.IDENTIFIER, l.word)
+
+-- Operators.
+local operator = token(l.OPERATOR, S('`~@$%^&*-+/=\\<>?.,:;()[]{}'))
+
+M._rules = {
+  {'whitespace', ws},
+  {'keyword', keyword},
+  {'type', type},
+  {'identifier', identifier},
+  {'string', string},
+  {'comment', comment},
+  {'number', number},
+  {'operator', operator},
+}
+
+M._foldsymbols = {
+  _patterns = {'[%(%)]', '/%*', '%*/', '#', '//'},
+  [l.OPERATOR] = {['('] = 1, [')'] = -1},
+  [l.COMMENT] = {
+    ['/*'] = 1, ['*/'] = -1, ['#'] = l.fold_line_comments('#'),
+    ['//'] = l.fold_line_comments('//')
+  }
+}
+
+return M