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, 56 insertions, 0 deletions

diff --git a/lua/lexers/gap.lua b/lua/lexers/gap.lua
new file mode 100644
index 0000000..3d9f7a4
--- /dev/null
+++ b/lua/lexers/gap.lua
@@ -0,0 +1,56 @@
+-- Copyright 2006-2016 Mitchell mitchell.att.foicica.com. See LICENSE.
+-- Gap 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 = 'gap'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Comments.
+local comment = token(l.COMMENT, '#' * l.nonnewline^0)
+
+-- Strings.
+local sq_str = l.delimited_range("'", true)
+local dq_str = l.delimited_range('"', true)
+local string = token(l.STRING, sq_str + dq_str)
+
+-- Numbers.
+local number = token(l.NUMBER, l.digit^1 * -l.alpha)
+
+-- Keywords.
+local keyword = token(l.KEYWORD, word_match{
+  'and', 'break', 'continue', 'do', 'elif', 'else', 'end', 'fail', 'false',
+  'fi', 'for', 'function', 'if', 'in', 'infinity', 'local', 'not', 'od', 'or',
+  'rec', 'repeat', 'return', 'then', 'true', 'until', 'while'
+})
+
+-- Identifiers.
+local identifier = token(l.IDENTIFIER, l.word)
+
+-- Operators.
+local operator = token(l.OPERATOR, S('*+-,./:;<=>~^#()[]{}'))
+
+M._rules = {
+  {'whitespace', ws},
+  {'keyword', keyword},
+  {'identifier', identifier},
+  {'string', string},
+  {'comment', comment},
+  {'number', number},
+  {'operator', operator},
+}
+
+M._foldsymbols = {
+  _patterns = {'[a-z]+', '#'},
+  [l.KEYWORD] = {
+    ['function'] = 1, ['end'] = -1, ['do'] = 1, od = -1, ['if'] = 1, fi = -1,
+    ['repeat'] = 1, ['until'] = -1
+  },
+  [l.COMMENT] = {['#'] = l.fold_line_comments('#')}
+}
+
+return M