x86, ptrace: fix build breakage with gcc 4.7 (second try)

syscall_trace_enter() and syscall_trace_leave() are only called from
within asm code and do not need to be declared in the .c at all.
Removing their reference fixes the build issue that was happening
with gcc 4.7.

Both Sven-Haegar Koch and Christoph Biedl confirmed this patch
addresses their respective build issues.

Cc: Sven-Haegar Koch <haegar@sdinet.de>
Cc: Christoph Biedl <linux-kernel.bfrz@manchmal.in-ulm.de>
Signed-off-by: Willy Tarreau <w@1wt.eu>

arch/x86/include/asm/ptrace.h

@@ -142,9 +142,6 @@ extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
 			 int error_code, int si_code);
 void signal_fault(struct pt_regs *regs, void __user *frame, char *where);
 
-extern long syscall_trace_enter(struct pt_regs *);
-extern void syscall_trace_leave(struct pt_regs *);
-
 static inline unsigned long regs_return_value(struct pt_regs *regs)
 {
 	return regs->ax;