Fix some typos.

contrib/puff/puff.c

@@ -17,7 +17,7 @@
  * All dynamically allocated memory comes from the stack.  The stack required
  * is less than 2K bytes.  This code is compatible with 16-bit int's and
  * assumes that long's are at least 32 bits.  puff.c uses the short data type,
- * assumed to be 16 bits, for arrays in order to to conserve memory.  The code
+ * assumed to be 16 bits, for arrays in order to conserve memory.  The code
  * works whether integers are stored big endian or little endian.
  *
  * In the comments below are "Format notes" that describe the inflate process