fix typos in texi files for documentation build

doc/manual/tracing.texi

@@ -812,7 +812,7 @@ using pcap tracing in the @code{Ipv4} protocol.  Each protocol helper enabling t
 methods must implement a single virtual method inherited from this class.  There
 will be a separate implementation for @code{Ipv6}, for example, but the only
 difference will be in the method names and signatures.  Different method names
-are required to disambiguate class @code{Ipv4} from @coe{Ipv6} which are both 
+are required to disambiguate class @code{Ipv4} from @code{Ipv6} which are both 
 derived from class @code{Object}, and methods that share the same signature.
 
 @verbatim

doc/testing/testing-framework.texi

@@ -562,7 +562,7 @@ a @code{--tempdir}, so the test runner will figure one out for you if you don't
 provide one.  It first looks for environment variables named @code{TMP} and 
 @code{TEMP} and uses those.  If neither @code{TMP} nor @code{TEMP} are defined
 it picks @code{/tmp}.  The code then tacks on an identifier indicating what 
-created the directory (ns-3) then the time (hh.mm.ss} followed by a large random
+created the directory (ns-3) then the time (hh.mm.ss) followed by a large random
 number.  The test runner creates a directory of that name to be used as the
 temporary directory.  Temporary files then go into a directory that will be
 named something like,

doc/tutorial/tracing.texi

@@ -2083,7 +2083,7 @@ passed around (a @code{Ptr<PcapFileWrapper>}) represents a pcap file.  There
 is a one-liner in the trace sink to write a timestamp and the contents of the 
 packet being dropped to the pcap file:
 
-@end verbatim
+@verbatim
   file->Write(Simulator::Now(), p);
 @end verbatim