Pipes cannot use SOCK_DGRAM. Back to SOCK_STREAM.

Add debugging to fdwait.

Rewrite getcallerpc on PowerMac to be correct.

src/lib9/getcallerpc-PowerMacintosh.c

@@ -0,0 +1,7 @@
+#include <lib9.h>
+
+ulong
+getcallerpc(void *x)
+{
+	return (((ulong*)(x))[-4]);
+}

src/lib9/getcallerpc-PowerMacintosh.s

@@ -1,5 +0,0 @@
-.text
-.globl _getcallerpc
-_getcallerpc:
-	mflr	r3
-	blr

src/lib9/pipe.c

@@ -6,5 +6,5 @@
 int
 p9pipe(int fd[2])
 {
-	return socketpair(AF_UNIX, SOCK_DGRAM, 0, fd);
+	return socketpair(AF_UNIX, SOCK_STREAM, 0, fd);
 }