Fix markup.

Sponsored by:	The FreeBSD Foundation

lib/libc/sys/_umtx_op.2

@@ -472,7 +472,7 @@ read of the umutex memory faults
 .It
 the list length limit described in
 .Xr libthr 3
- is reached.
+is reached.
 .El
 .Pp
 Every mutex in both lists is unlocked as if the

lib/libthr/libthr.3

@@ -234,7 +234,7 @@ installs interposing handlers into the hooks exported by
 .Li libc .
 The interposers provide real locking implementation instead of the
 stubs for single-threaded processes in
-.Li ,
+.Li libc ,
 cancellation support and some modifications to the signal operations.
 .Pp
 .Nm