Fix inttypes.h circular include: use stdint.h+stddef.h instead of wchar.h

inttypes.h included wchar.h for wchar_t and stdint.h, but this created
a circular dependency: wchar.h → stdint.h → gnulib inttypes.h →
inttypes.h → wchar.h. When gnulib's wchar.h wrapper was re-entered
during this cycle, wint_t and mbstate_t were not yet defined.

POSIX spec says inttypes.h should include stdint.h directly and
wchar_t comes from stddef.h. Using stdint.h + stddef.h breaks the
circular chain at its source.

src/header/inttypes/cbindgen.toml

@@ -4,8 +4,10 @@
 # - "The <inttypes.h> header shall include the <stdint.h> header."
 # - "wchar_t As described in <stddef.h>."
 #
-# wchar.h brings in both stdint.h and stddef.h
-sys_includes = ["wchar.h"]
+# Include stdint.h and stddef.h directly per POSIX spec.
+# Do NOT include wchar.h — it creates a circular dependency:
+#   wchar.h → stdint.h → gnulib inttypes.h → inttypes.h → wchar.h
+sys_includes = ["stdint.h", "stddef.h"]
 include_guard = "_RELIBC_INTTYPES_H"
 trailer = """
 #ifndef _RELIBC_BITS_INTTYPES_H