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, 45 insertions, 0 deletions

diff --git a/lua/lexers/tex.lua b/lua/lexers/tex.lua
new file mode 100644
index 0000000..ec1e717
--- /dev/null
+++ b/lua/lexers/tex.lua
@@ -0,0 +1,45 @@
+-- Copyright 2006-2016 Mitchell mitchell.att.foicica.com. See LICENSE.
+-- Plain TeX LPeg lexer.
+-- Modified by Robert Gieseke.
+
+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 = 'tex'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Comments.
+local comment = token(l.COMMENT, '%' * l.nonnewline^0)
+
+-- TeX environments.
+local environment = token('environment', '\\' * (P('begin') + 'end') * l.word)
+
+-- Commands.
+local command = token(l.KEYWORD, '\\' * (l.alpha^1 + S('#$&~_^%{}')))
+
+-- Operators.
+local operator = token(l.OPERATOR, S('$&#{}[]'))
+
+M._rules = {
+  {'whitespace', ws},
+  {'comment', comment},
+  {'environment', environment},
+  {'keyword', command},
+  {'operator', operator},
+}
+
+M._tokenstyles = {
+  environment = l.STYLE_KEYWORD
+}
+
+M._foldsymbols = {
+  _patterns = {'\\begin', '\\end', '[{}]', '%%'},
+  [l.COMMENT] = {['%'] = l.fold_line_comments('%')},
+  ['environment'] = {['\\begin'] = 1, ['\\end'] = -1},
+  [l.OPERATOR] = {['{'] = 1, ['}'] = -1}
+}
+
+return M