add vim swap file to .gitignore and t/whitespace.t's exempt list

Author: menghan

.gitignore

@@ -39,3 +39,4 @@ doc/protocol-binary.txt
 /timedrun
 /doc/doxy
 /memcached.spec
+.*.swp

t/whitespace.t

@@ -11,6 +11,7 @@ BEGIN {
     push(@exempted, glob("doc/xml2rfc/*.xsl"));
     push(@exempted, glob("m4/*backport*m4"));
     push(@exempted, glob("*.orig"));
+    push(@exempted, glob(".*.swp"));
     my %exempted_hash = map { $_ => 1 } @exempted;
 
     my @stuff = split /\0/, `git ls-files -z -c -m -o --exclude-standard`;