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, 64 insertions, 0 deletions

diff --git a/lua/lexers/gherkin.lua b/lua/lexers/gherkin.lua
new file mode 100644
index 0000000..c4f4dae
--- /dev/null
+++ b/lua/lexers/gherkin.lua
@@ -0,0 +1,64 @@
+-- Copyright 2015-2016 Jason Schindler. See LICENSE.
+-- Gherkin (https://github.com/cucumber/cucumber/wiki/Gherkin) 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 = 'gherkin'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Tags.
+local tag = token('tag', '@' * l.word^0)
+
+-- Comments.
+local comment = token(l.COMMENT, '#' * l.nonnewline^0)
+
+-- Strings.
+local doc_str = '"""' * (l.any - '"""')^0 * P('"""')^-1
+local dq_str = l.delimited_range('"')
+
+local string = token(l.STRING, doc_str + dq_str)
+
+-- Placeholders.
+local placeholder = token('placeholder', l.nested_pair('<', '>'))
+
+-- Keywords.
+local keyword = token(l.KEYWORD, word_match{
+  'Given', 'When', 'Then', 'And', 'But'
+})
+
+-- Identifiers.
+local identifier = token(l.KEYWORD, P('Scenario Outline') + word_match{
+  'Feature', 'Background', 'Scenario', 'Scenarios', 'Examples'
+})
+
+-- Examples.
+local example = token('example', '|' * l.nonnewline^0)
+
+-- Numbers.
+local number = token(l.NUMBER, l.float + l.integer)
+
+M._rules = {
+  {'whitespace', ws},
+  {'comment', comment},
+  {'tag', tag},
+  {'placeholder', placeholder},
+  {'keyword', keyword},
+  {'identifier', identifier},
+  {'example', example},
+  {'string', string},
+  {'number', number}
+}
+
+M._tokenstyles = {
+  tag = l.STYLE_LABEL,
+  placeholder = l.STYLE_NUMBER,
+  example = l.STYLE_NUMBER
+}
+
+M._FOLDBYINDENTATION = true
+
+return M