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, 69 insertions, 0 deletions

diff --git a/lua/lexers/apl.lua b/lua/lexers/apl.lua
new file mode 100644
index 0000000..4fa492e
--- /dev/null
+++ b/lua/lexers/apl.lua
@@ -0,0 +1,69 @@
+-- Copyright 2015-2016 David B. Lamkins <david@lamkins.net>. See LICENSE.
+-- APL 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 = 'apl'}
+
+-- Whitespace.
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Comments.
+local comment = token(l.COMMENT, (P('⍝') + P('#')) * l.nonnewline^0)
+
+-- Strings.
+local sq_str = l.delimited_range("'", false, true)
+local dq_str = l.delimited_range('"')
+
+local string = token(l.STRING, sq_str + dq_str)
+
+-- Numbers.
+local dig = R('09')
+local rad = P('.')
+local exp = S('eE')
+local img = S('jJ')
+local sgn = P('¯')^-1
+local float = sgn * (dig^0 * rad * dig^1 + dig^1 * rad * dig^0 + dig^1) *
+              (exp * sgn *dig^1)^-1
+local number = token(l.NUMBER, float * img * float + float)
+
+-- Keywords.
+local keyword = token(l.KEYWORD, P('⍞') + P('χ') + P('⍺') + P('⍶') + P('⍵') +
+                                 P('⍹') + P('⎕') * R('AZ', 'az')^0)
+
+-- Names.
+local n1l = R('AZ', 'az')
+local n1b = P('_') + P('∆') + P('⍙')
+local n2l = n1l + R('09')
+local n2b = n1b + P('¯')
+local n1 = n1l + n1b
+local n2 = n2l + n2b
+local name = n1 * n2^0
+
+-- Labels.
+local label = token(l.LABEL, name * P(':'))
+
+-- Variables.
+local variable = token(l.VARIABLE, name)
+
+-- Special.
+local special = token(l.TYPE, S('{}[]();') + P('←') + P('→') + P('◊'))
+
+-- Nabla.
+local nabla = token(l.PREPROCESSOR, P('∇') + P('⍫'))
+
+M._rules = {
+  {'whitespace', ws},
+  {'comment', comment},
+  {'string', string},
+  {'number', number},
+  {'keyword', keyword},
+  {'label', label},
+  {'variable', variable},
+  {'special', special},
+  {'nabla', nabla},
+}
+
+return M