Adapt to linux-wrs kernel version, which has character '_' inside.

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>

diff -ruN dpkg-1.15.8.5-orig/lib/dpkg/parsehelp.c dpkg-1.15.8.5/lib/dpkg/parsehelp.c
--- dpkg-1.15.8.5-orig/lib/dpkg/parsehelp.c	2010-10-08 12:27:15.058572774 +0800
+++ dpkg-1.15.8.5/lib/dpkg/parsehelp.c	2010-10-09 11:18:15.484190771 +0800
@@ -268,11 +268,11 @@
 
   /* XXX: Would be faster to use something like cisversion and cisrevision. */
   for (ptr = rversion->version; *ptr; ptr++) {
-    if (!cisdigit(*ptr) && !cisalpha(*ptr) && strchr(".-+~:", *ptr) == NULL)
+    if (!cisdigit(*ptr) && !cisalpha(*ptr) && strchr(".-+~:_", *ptr) == NULL)
       return _("invalid character in version number");
   }
   for (ptr = rversion->revision; *ptr; ptr++) {
-    if (!cisdigit(*ptr) && !cisalpha(*ptr) && strchr(".-+~", *ptr) == NULL)
+    if (!cisdigit(*ptr) && !cisalpha(*ptr) && strchr(".-+~_", *ptr) == NULL)
       return _("invalid character in revision number");
   }
 
