[build] Move headers out of target dirs

The great header shift: It didn't make sense to regenerate headers for
the same module for every target (boot/kernel/user) it appeared in. And
now that core headers are out of src/include, this was going to cause
problems for the new libc changes I've been working on. So I went back
to re-design how module headers work.

Pre-requisites:
- A module's public headers should all be available in one location, not
  tied to target.
- No accidental includes. Another module should not be able to include
  anything (creating an implicit dependency) from a module without
  declaring an explicit dependency.
- Exception to the previous: libc's headers should be available to all,
  at least for the freestanding headers.

New system:
- A new "public_headers" property of module declares all public headers
  that should be available to dependant modules
- All public headers (after possible processing) are installed relative
  to build/include/<module> with the same path as their source
- This also means no "include" dir in modules is necessary. If a header
  should be included as <j6/types.h> then its source should be
  src/libraries/j6/j6/types.h - this caused the most churn as all public
  header sources moved one directory up.
- The "includes" property of a module is local only to that module now,
  it does not create any implicit public interface

Other changes:
- The bonnibel concept of sources changed: instead of sources having
  actions, they themselves are an instance of a (sub)class of Source,
  which provides all the necessary information itself.
- Along with the above, rule names were standardized into <type>.<ext>,
  eg "compile.cpp" or "parse.cog"
- cog and cogflags variables moved from per-target scope to global scope
  in the build files.
- libc gained a more dynamic .module file

src/libraries/libc/wchar.h

@@ -0,0 +1,91 @@
+#pragma once
+/* Wide character functions <wchar.h>
+*/
+
+#include "j6libc/cpp.h"
+#include "j6libc/int.h"
+#include "j6libc/null.h"
+#include "j6libc/size_t.h"
+#include "j6libc/wchar_t.h"
+#include "j6libc/wctype_t.h"
+#include "j6libc/wint_t.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+
+CPP_CHECK_BEGIN
+
+typedef unsigned long mbstate_t;
+
+wint_t btowc(int);
+int fwprintf(FILE *, const wchar_t *, ...);
+int fwscanf(FILE *, const wchar_t *, ...);
+int iswalnum(wint_t);
+int iswalpha(wint_t);
+int iswcntrl(wint_t);
+int iswdigit(wint_t);
+int iswgraph(wint_t);
+int iswlower(wint_t);
+int iswprint(wint_t);
+int iswpunct(wint_t);
+int iswspace(wint_t);
+int iswupper(wint_t);
+int iswxdigit(wint_t);
+int iswctype(wint_t, wctype_t);
+wint_t fgetwc(FILE *);
+wchar_t *fgetws(wchar_t *, int, FILE *);
+wint_t fputwc(wchar_t, FILE *);
+int fputws(const wchar_t *, FILE *);
+int fwide(FILE *, int);
+wint_t getwc(FILE *);
+wint_t getwchar(void);
+int mbsinit(const mbstate_t *);
+size_t mbrlen(const char *, size_t, mbstate_t *);
+size_t mbrtowc(wchar_t *, const char *, size_t, mbstate_t *);
+size_t mbsrtowcs(wchar_t *, const char **, size_t, mbstate_t *);
+wint_t putwc(wchar_t, FILE *);
+wint_t putwchar(wchar_t);
+int swprintf(wchar_t *, size_t, const wchar_t *, ...);
+int swscanf(const wchar_t *, const wchar_t *, ...);
+wint_t towlower(wint_t);
+wint_t towupper(wint_t);
+wint_t ungetwc(wint_t, FILE *);
+int vfwprintf(FILE *, const wchar_t *, va_list);
+int vwprintf(const wchar_t *, va_list);
+int vswprintf(wchar_t *, size_t, const wchar_t *, va_list);
+size_t wcrtomb(char *, wchar_t, mbstate_t *);
+wchar_t *wcscat(wchar_t *, const wchar_t *);
+wchar_t *wcschr(const wchar_t *, wchar_t);
+int wcscmp(const wchar_t *, const wchar_t *);
+int wcscoll(const wchar_t *, const wchar_t *);
+wchar_t *wcscpy(wchar_t *, const wchar_t *);
+size_t wcscspn(const wchar_t *, const wchar_t *);
+size_t wcsftime(wchar_t *, size_t, const wchar_t *, const struct tm *);
+size_t wcslen(const wchar_t *);
+wchar_t *wcsncat(wchar_t *, const wchar_t *, size_t);
+int wcsncmp(const wchar_t *, const wchar_t *, size_t);
+wchar_t *wcsncpy(wchar_t *, const wchar_t *, size_t);
+wchar_t *wcspbrk(const wchar_t *, const wchar_t *);
+wchar_t *wcsrchr(const wchar_t *, wchar_t);
+size_t wcsrtombs(char *, const wchar_t **, size_t, mbstate_t *);
+size_t wcsspn(const wchar_t *, const wchar_t *);
+wchar_t *wcsstr(const wchar_t *, const wchar_t *);
+double wcstod(const wchar_t *, wchar_t **);
+wchar_t *wcstok(wchar_t *, const wchar_t *, wchar_t **);
+long int wcstol(const wchar_t *, wchar_t **, int);
+unsigned long int wcstoul(const wchar_t *, wchar_t **, int);
+wchar_t *wcswcs(const wchar_t *, const wchar_t *);
+int wcswidth(const wchar_t *, size_t);
+size_t wcsxfrm(wchar_t *, const wchar_t *, size_t);
+int wctob(wint_t);
+wctype_t wctype(const char *);
+int wcwidth(wchar_t);
+wchar_t *wmemchr(const wchar_t *, wchar_t, size_t);
+int wmemcmp(const wchar_t *, const wchar_t *, size_t);
+wchar_t *wmemcpy(wchar_t *, const wchar_t *, size_t);
+wchar_t *wmemmove(wchar_t *, const wchar_t *, size_t);
+wchar_t *wmemset(wchar_t *, wchar_t, size_t);
+int wprintf(const wchar_t *, ...);
+int wscanf(const wchar_t *, ...);
+
+CPP_CHECK_END