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/lpeglabel/lpcap.h

@@ -0,0 +1,43 @@
+/*
+** $Id: lpcap.h,v 1.2 2015/02/27 17:13:17 roberto Exp $
+*/
+
+#if !defined(lpcap_h)
+#define lpcap_h
+
+
+#include "lptypes.h"
+
+
+/* kinds of captures */
+typedef enum CapKind {
+  Cclose, Cposition, Cconst, Cbackref, Carg, Csimple, Ctable, Cfunction,
+  Cquery, Cstring, Cnum, Csubst, Cfold, Cruntime, Cgroup
+} CapKind;
+
+
+typedef struct Capture {
+  const char *s;  /* subject position */
+  unsigned short idx;  /* extra info (group name, arg index, etc.) */
+  byte kind;  /* kind of capture */
+  byte siz;  /* size of full capture + 1 (0 = not a full capture) */
+} Capture;
+
+
+typedef struct CapState {
+  Capture *cap;  /* current capture */
+  Capture *ocap;  /* (original) capture list */
+  lua_State *L;
+  int ptop;  /* index of last argument to 'match' */
+  const char *s;  /* original string */
+  int valuecached;  /* value stored in cache slot */
+} CapState;
+
+
+int runtimecap (CapState *cs, Capture *close, const char *s, int *rem);
+int getcaptures (lua_State *L, const char *s, const char *r, int ptop);
+int finddyncap (Capture *cap, Capture *last);
+
+#endif
+
+