sip/sip_extra_headers.txt: fixed whitespace

darcs-hash:20081127232538-db55f-d142cb5e8b5a1e29639777f31b277bffb912e9d0.gz

libsofia-sip-ua/sip/sip_extra_headers.txt

@@ -4,7 +4,7 @@
 # The parsed headers are accessed with function (or macro) like sip_refer_sub()
 # e.g., sip_refer_sub_t *rsub = sip_refer_sub(sip);
 #
-# The line format is: 
+# The line format is:
 # C-name @SINCE sip_t-like-comment
 #
 # Put all experimental things after EXPERIMENTAL HEADER LIST STARTS HERE...