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, 53 insertions, 0 deletions

diff --git a/lua/lexers/pico8.lua b/lua/lexers/pico8.lua
new file mode 100644
index 0000000..44364f3
--- /dev/null
+++ b/lua/lexers/pico8.lua
@@ -0,0 +1,53 @@
+-- Copyright 2016 Alejandro Baez (https://keybase.io/baez). See LICENSE.
+-- PICO-8 Lexer.
+-- http://www.lexaloffle.com/pico-8.php
+
+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 = 'pico8'}
+
+-- Whitespace
+local ws = token(l.WHITESPACE, l.space^1)
+
+-- Comments
+local comment = token(l.COMMENT, '//' * l.nonnewline_esc^0)
+
+-- Numbers
+local number = token(l.NUMBER, l.integer)
+
+-- Keywords
+local keyword = token(l.KEYWORD, word_match{
+  '__lua__', '__gfx__', '__gff__', '__map__', '__sfx__', '__music__'
+})
+
+-- Identifiers
+local identifier = token(l.IDENTIFIER, l.word)
+
+-- Operators
+local operator = token(l.OPERATOR, S('_'))
+
+M._rules = {
+  {'whitespace', ws},
+  {'keyword', keyword},
+  {'identifier', identifier},
+  {'comment', comment},
+  {'number', number},
+  {'operator', operator},
+}
+
+-- Embed Lua into PICO-8.
+local lua = l.load('lua')
+
+local lua_start_rule = token('pico8_tag', '__lua__')
+local lua_end_rule = token('pico8_tag', '__gfx__' )
+l.embed_lexer(M, lua, lua_start_rule, lua_end_rule)
+
+M._tokenstyles = {
+  pico8_tag = l.STYLE_EMBEDDED
+}
+
+M._foldsymbols = lua._foldsymbols
+
+return M