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/protobuf.lua b/lua/lexers/protobuf.lua
new file mode 100644
index 0000000..c257e7e
--- /dev/null
+++ b/lua/lexers/protobuf.lua
@@ -0,0 +1,58 @@
+-- Copyright 2016 David B. Lamkins <david@lamkins.net>. See LICENSE.
+-- Protocol Buffer IDL LPeg lexer.
+-- <https://developers.google.com/protocol-buffers/>
+
+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 = 'protobuf'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Comments.
+local line_comment = '//' * l.nonnewline_esc^0
+local block_comment = '/*' * (l.any - '*/')^0 * P('*/')^-1
+local comment = token(l.COMMENT, line_comment + block_comment)
+
+-- Strings.
+local sq_str = P('L')^-1 * l.delimited_range("'", true)
+local dq_str = P('L')^-1 * l.delimited_range('"', true)
+local string = token(l.STRING, sq_str + dq_str)
+
+-- Numbers.
+local number = token(l.NUMBER, l.float + l.integer)
+
+-- Keywords.
+local keyword = token(l.KEYWORD, word_match{
+  'contained', 'syntax', 'import', 'option', 'package', 'message', 'group',
+  'oneof', 'optional', 'required', 'repeated', 'default', 'extend',
+  'extensions', 'to', 'max', 'reserved', 'service', 'rpc', 'returns'
+})
+
+-- Types.
+local type = token(l.TYPE, word_match{
+  'int32', 'int64', 'uint32', 'uint64', 'sint32', 'sint64', 'fixed32',
+  'fixed64', 'sfixed32', 'sfixed64', 'float', 'double', 'bool', 'string',
+  'bytes', 'enum', 'true', 'false'
+})
+
+-- 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},
+}
+
+return M