use I not IR for single arguments

Reference: /n/sources/patch/maybe/venti-mannit
Date: Sun Dec  2 18:38:59 CET 2012
Signed-off-by: quanstro@quanstro.net

--- /sys/man/2/venti-client	Sun Dec  2 18:38:43 2012
+++ /sys/man/2/venti-client	Sun Dec  2 18:38:42 2012
@@ -59,7 +59,7 @@
 .I Vtrpc
 executes a single Venti RPC transaction, sending the request 
 packet
-.IR p
+.I p
 and then waiting for and returning the response packet.
 .I Vtrpc
 will set the tag in the packet.
--- /sys/man/2/venti-conn	Sun Dec  2 18:38:45 2012
+++ /sys/man/2/venti-conn	Sun Dec  2 18:38:44 2012
@@ -102,7 +102,7 @@
 on the connection
 .IR z .
 The packet
-.IR p
+.I p
 should be a formatted Venti message as might
 be returned by
 .IR vtfcallpack ;
--- /sys/man/2/venti-file	Sun Dec  2 18:38:48 2012
+++ /sys/man/2/venti-file	Sun Dec  2 18:38:46 2012
@@ -135,7 +135,7 @@
 and
 .BR VtORDWR
 modes can only be used if
-.IR f
+.I f
 is open with mode
 .BR VtORDWR .
 .PP
--- /sys/man/2/venti-packet	Sun Dec  2 18:38:50 2012
+++ /sys/man/2/venti-packet	Sun Dec  2 18:38:49 2012
@@ -122,7 +122,7 @@
 .IR p .
 This may be larger than the number of bytes stored
 in
-.IR p
+.I p
 because fragments may not be filled completely.
 .PP
 .I Packetcmp