Use SIGUSR1 instead of SIGSTOP to suspend threads.

diff --git a/server/context_i386.c b/server/context_i386.c
index b7a7bb0..75028cf 100644
--- a/server/context_i386.c
+++ b/server/context_i386.c
@@ -534,7 +534,7 @@
     if (suspend_for_ptrace( thread ))
     {
         get_thread_context( thread, CONTEXT_CONTROL, &context );
-        resume_thread( thread );
+        resume_after_ptrace( thread );
     }
     return (void *)context.Eip;
 }
@@ -576,7 +576,7 @@
         if (flags && suspend_for_ptrace( thread ))
         {
             get_thread_context( thread, flags, data );
-            resume_thread( thread );
+            resume_after_ptrace( thread );
         }
     }
     release_object( thread );
@@ -604,7 +604,7 @@
         if (flags && suspend_for_ptrace( thread ))
         {
             set_thread_context( thread, flags, get_req_data() );
-            resume_thread( thread );
+            resume_after_ptrace( thread );
         }
         release_object( thread );
     }