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, 58 insertions, 0 deletions

diff --git a/lua/lexers/bibtex.lua b/lua/lexers/bibtex.lua
new file mode 100644
index 0000000..b47770c
--- /dev/null
+++ b/lua/lexers/bibtex.lua
@@ -0,0 +1,58 @@
+-- Copyright 2006-2016 Mitchell mitchell.att.foicica.com. See LICENSE.
+-- Bibtex 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 = 'bibtex'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Strings.
+local string = token(l.STRING, l.delimited_range('"') +
+                               l.delimited_range('{}', false, true, true))
+
+-- Fields.
+local field = token('field', word_match{
+  'author', 'title', 'journal', 'year', 'volume', 'number', 'pages', 'month',
+  'note', 'key', 'publisher', 'editor', 'series', 'address', 'edition',
+  'howpublished', 'booktitle', 'organization', 'chapter', 'school',
+  'institution', 'type', 'isbn', 'issn', 'affiliation', 'issue', 'keyword',
+  'url'
+})
+
+-- Identifiers.
+local identifier = token(l.IDENTIFIER, l.word)
+
+-- Operators.
+local operator = token(l.OPERATOR, S(',='))
+
+M._rules = {
+  {'whitespace', ws},
+  {'field', field},
+  {'identifier', identifier},
+  {'string', string},
+  {'operator', operator},
+}
+
+-- Embedded in Latex.
+local latex = l.load('latex')
+
+-- Embedded Bibtex.
+local entry = token('entry', P('@') * word_match({
+  'book', 'article', 'booklet', 'conference', 'inbook', 'incollection',
+  'inproceedings', 'manual', 'mastersthesis', 'lambda', 'misc', 'phdthesis',
+  'proceedings', 'techreport', 'unpublished'
+}, nil, true))
+local bibtex_start_rule = entry * ws^0 * token(l.OPERATOR, P('{'))
+local bibtex_end_rule = token(l.OPERATOR, P('}'))
+l.embed_lexer(latex, M, bibtex_start_rule, bibtex_end_rule)
+
+M._tokenstyles = {
+  field = l.STYLE_CONSTANT,
+  entry = l.STYLE_PREPROCESSOR
+}
+
+return M