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, 87 insertions, 0 deletions

diff --git a/lua/lexers/cpp.lua b/lua/lexers/cpp.lua
new file mode 100644
index 0000000..518fe64
--- /dev/null
+++ b/lua/lexers/cpp.lua
@@ -0,0 +1,87 @@
+-- Copyright 2006-2016 Mitchell mitchell.att.foicica.com. See LICENSE.
+-- C++ 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 = 'cpp'}
+
+-- 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)
+
+-- Preprocessor.
+local preproc_word = word_match{
+  'define', 'elif', 'else', 'endif', 'error', 'if', 'ifdef', 'ifndef', 'import',
+  'include', 'line', 'pragma', 'undef', 'using', 'warning'
+}
+local preproc = token(l.PREPROCESSOR,
+                      l.starts_line('#') * S('\t ')^0 * preproc_word)
+
+-- Keywords.
+local keyword = token(l.KEYWORD, word_match{
+  'asm', 'auto', 'break', 'case', 'catch', 'class', 'const', 'const_cast',
+  'continue', 'default', 'delete', 'do', 'dynamic_cast', 'else', 'explicit',
+  'export', 'extern', 'false', 'for', 'friend', 'goto', 'if', 'inline',
+  'mutable', 'namespace', 'new', 'operator', 'private', 'protected', 'public',
+  'register', 'reinterpret_cast', 'return', 'sizeof', 'static', 'static_cast',
+  'switch', 'template', 'this', 'throw', 'true', 'try', 'typedef', 'typeid',
+  'typename', 'using', 'virtual', 'volatile', 'while',
+  -- Operators
+  'and', 'and_eq', 'bitand', 'bitor', 'compl', 'not', 'not_eq', 'or', 'or_eq',
+  'xor', 'xor_eq',
+  -- C++11
+  'alignas', 'alignof', 'constexpr', 'decltype', 'final', 'noexcept',
+  'override', 'static_assert', 'thread_local'
+})
+
+-- Types.
+local type = token(l.TYPE, word_match{
+  'bool', 'char', 'double', 'enum', 'float', 'int', 'long', 'short', 'signed',
+  'struct', 'union', 'unsigned', 'void', 'wchar_t',
+  -- C++11
+  'char16_t', 'char32_t', 'nullptr'
+})
+
+-- 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},
+  {'preproc', preproc},
+  {'operator', operator},
+}
+
+M._foldsymbols = {
+  _patterns = {'%l+', '[{}]', '/%*', '%*/', '//'},
+  [l.PREPROCESSOR] = {
+    region = 1, endregion = -1,
+    ['if'] = 1, ifdef = 1, ifndef = 1, endif = -1
+  },
+  [l.OPERATOR] = {['{'] = 1, ['}'] = -1},
+  [l.COMMENT] = {['/*'] = 1, ['*/'] = -1, ['//'] = l.fold_line_comments('//')}
+}
+
+return M