Implement raise () in libc

The core functionality (i.e., the equivalent of `kill (getpid (), sig);`)
was already there in the implementation of `abort ()`. Now, it got
factored out to `raise ()` so that others (most importantly,
`__aeabi_ldiv0`) can call and link to it as well.

Also, removed `LIBC_UNREACHABLE_STUB_FOR` macro, as it is not used anymore.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-libc/jerry-libc-defs.h

@@ -54,19 +54,4 @@ libc_fatal (const char *msg,
    } while (0)
 #endif /* !LIBC_NDEBUG */
 
-/**
- * Stubs declaration
- */
-
-/**
- * Unreachable stubs for routines that are never called,
- * but referenced from third-party libraries.
- */
-#define LIBC_UNREACHABLE_STUB_FOR(...) \
-extern __VA_ARGS__; \
-__attr_used___ __VA_ARGS__ \
-{ \
-  LIBC_UNREACHABLE (); \
-}
-
 #endif /* !DEFS_H */