Move all ptrace-related macros and declarations from defs.h to ptrace.h

* ptrace.h: New file.
* Makefile.am (strace_SOURCES): Add it.
* configure.ac (AC_CHECK_HEADERS): Remove linux/ptrace.h and sys/ptrace.h.
* defs.h: Do not include <sys/ptrace.h> and <asm/ptrace.h>.
Remove definitions of PTRACE_* macros.
* process.c: Remove <linux/ptrace.h> workarounds, include "ptrace.h".
* signal.c: Likewise.
* syscall.c: Likewise.
* util.c: Likewise.
* strace.c: Include "ptrace.h".
* wait.c: Likewise.
diff --git a/signal.c b/signal.c
index 6dd2469..8fd91b6 100644
--- a/signal.c
+++ b/signal.c
@@ -32,29 +32,14 @@
  */
 
 #include "defs.h"
-#include <sys/user.h>
 #include <fcntl.h>
+#include <sys/user.h>
 
 #ifdef HAVE_SYS_REG_H
 # include <sys/reg.h>
 #endif
 
-#ifdef HAVE_LINUX_PTRACE_H
-# undef PTRACE_SYSCALL
-# ifdef HAVE_STRUCT_IA64_FPREG
-#  define ia64_fpreg XXX_ia64_fpreg
-# endif
-# ifdef HAVE_STRUCT_PT_ALL_USER_REGS
-#  define pt_all_user_regs XXX_pt_all_user_regs
-# endif
-# ifdef HAVE_STRUCT_PTRACE_PEEKSIGINFO_ARGS
-#  define ptrace_peeksiginfo_args XXX_ptrace_peeksiginfo_args
-# endif
-# include <linux/ptrace.h>
-# undef ptrace_peeksiginfo_args
-# undef ia64_fpreg
-# undef pt_all_user_regs
-#endif
+#include "ptrace.h"
 
 #ifdef IA64
 # include <asm/ptrace_offsets.h>