Add stage 06: Lua bootstrap

The goal of stage 06 is to try parse zig synax in lua. I pulled in
lpeglable 1.2.0 and parser-gen off github to get started. All of this
needs to be cleaned up rather soon.

Lua boostraps using tcc and musl from the previous stage. Since musl
0.6.0 doesn't support dynamic linking this build of lua doesn't support
shared libraries. I couldn't easily patch musl with dlopen and friends
so instead I link statically and call deps with c api.

06/parser-gen/parsers/tiny-parser.lua

@@ -0,0 +1,55 @@
+package.path = package.path .. ";../?.lua"
+local pg = require "parser-gen"
+local peg = require "peg-parser"
+local errs = {errMissingThen = "Missing Then"}
+pg.setlabels(errs)
+
+
+local grammar = pg.compile([[
+
+  program <- stmtsequence !. 
+  stmtsequence <- statement (';' statement)* 
+  statement <- ifstmt / repeatstmt / assignstmt / readstmt / writestmt
+  ifstmt <- 'if' exp 'then'^errMissingThen stmtsequence elsestmt? 'end' 
+  elsestmt <- ('else' stmtsequence)
+  repeatstmt <-  'repeat' stmtsequence 'until' exp 
+  assignstmt <- IDENTIFIER ':=' exp 
+  readstmt <-  'read'  IDENTIFIER 
+  writestmt <-  'write' exp 
+  exp <-  simpleexp (COMPARISONOP simpleexp)*
+  COMPARISONOP <- '<' / '='
+  simpleexp <-  term (ADDOP term)* 
+  ADDOP <- [+-]
+  term <-  factor (MULOP factor)*
+  MULOP <- [*/]
+  factor <- '(' exp ')' / NUMBER / IDENTIFIER
+
+  NUMBER <- '-'? [0-9]+
+  KEYWORDS <- 'if' / 'repeat' / 'read' / 'write' / 'then' / 'else' / 'end' / 'until' 
+  RESERVED <- KEYWORDS ![a-zA-Z]
+  IDENTIFIER <- !RESERVED [a-zA-Z]+
+  HELPER <- ';' / %nl / %s / KEYWORDS / !.
+  SYNC <- (!HELPER .)*
+
+]], _, true)
+local errors = 0
+local function printerror(desc,line,col,sfail,trec)
+	errors = errors+1
+	print("Error #"..errors..": "..desc.." on line "..line.."(col "..col..")")
+end
+
+
+local function parse(input)
+	errors = 0
+	result, errors = pg.parse(input,grammar,printerror)
+	return result, errors
+end
+
+if arg[1] then	
+	-- argument must be in quotes if it contains spaces
+	res, errs = parse(arg[1])
+	peg.print_t(res)
+	peg.print_r(errs)
+end
+local ret = {parse=parse}
+return ret