Add sys/ucontext.h

* Move ucontext_t and mcontext_t there as that's where POSIX says they
should be.

headers/posix/signal.h

@@ -351,14 +351,4 @@ typedef struct vregs vregs;
 #include __HAIKU_ARCH_HEADER(signal.h)
 
 
-typedef struct vregs mcontext_t;
-
-typedef struct __ucontext_t {
-	struct __ucontext_t*	uc_link;
-	sigset_t				uc_sigmask;
-	stack_t					uc_stack;
-	mcontext_t				uc_mcontext;
-} ucontext_t;
-
-
 #endif /* _SIGNAL_H_ */

headers/posix/sys/ucontext.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2014, Haiku, Inc. All Rights Reserved.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _UCONTEXT_H_
+#define _UCONTEXT_H_
+
+
+typedef struct vregs mcontext_t;
+
+typedef struct __ucontext_t {
+	struct __ucontext_t*	uc_link;
+	sigset_t				uc_sigmask;
+	stack_t					uc_stack;
+	mcontext_t				uc_mcontext;
+} ucontext_t;
+
+
+#endif

headers/private/kernel/ksignal.h

@@ -17,6 +17,7 @@
 #include <heap.h>
 #include <util/DoublyLinkedList.h>
 #include <util/KernelReferenceable.h>
+#include <sys/ucontext.h>
 
 
 namespace BKernel {

headers/private/kernel/thread_types.h

@@ -25,6 +25,7 @@
 #include <util/DoublyLinkedList.h>
 #include <util/KernelReferenceable.h>
 #include <util/list.h>
+#include <sys/ucontext.h>
 
 
 enum additional_thread_state {