Merge branch 'sig_atomic_t' into 'master'

Move sig_atomic_t from stdint

See merge request redox-os/relibc!1205

include/stdint.h

@@ -374,6 +374,4 @@ typedef __UINTMAX_TYPE__ uintmax_t;
 #endif
 #endif
 
-typedef long sig_atomic_t;
-
 #endif /* _GCC_STDINT_H */

src/header/signal/cbindgen.toml

@@ -20,6 +20,7 @@ typedef struct siginfo siginfo_t;
 typedef unsigned long long sigset_t;
 typedef struct ucontext ucontext_t;
 typedef struct mcontext mcontext_t;
+typedef long sig_atomic_t;
 
 struct sigaction {
   union {