Fix pthread init and null for C++

src/header/bits_null/cbindgen.toml

@@ -9,3 +9,10 @@
 include_guard = "_RELIBC_BITS_NULL_T_H"
 language = "C"
 no_includes = true
+after_includes = """
+#ifdef __cplusplus
+  #define NULL nullptr
+#else
+  #define NULL ((void *)0)
+#endif
+"""

src/header/bits_null/mod.rs

@@ -1,4 +1 @@
-use crate::platform::types::c_long;
-
-/// Null pointer constant.
-pub const NULL: c_long = 0;
+// NULL is defined in cbindgen