Fixed typo in new 'p' description.

Doc/lib/libstruct.tex

@@ -100,7 +100,7 @@ The count is the total number of bytes stored.  The first byte stored is
 the length of the string, or 255, whichever is smaller.  The bytes
 of the string follow.  If the string passed in to \function{pack()} is too
 long (longer than the count minus 1), only the leading count-1 bytes of the
-string are stored,  If the string is shorter than count-1, it is padded
+string are stored.  If the string is shorter than count-1, it is padded
 with null bytes so that exactly count bytes in all are used.  Note that
 for \function{unpack()}, the \character{p} format character consumes count
 bytes, but that the string returned can never contain more than 255