Fix inflateInit2() bug when windowBits is 16 or 32.

A windowBits value of 0, 16, or 32 gets the window bits from the
zlib header.  However there is no zlib header for 16, or for 32
when the input is gzip.  This commit sets the window bits for
inflate to 15 if a gzip stream is detected and windowBits was 16
or 32.

inflate.c

@@ -645,6 +645,8 @@ int flush;
             NEEDBITS(16);
 #ifdef GUNZIP
             if ((state->wrap & 2) && hold == 0x8b1f) {  /* gzip header */
+                if (state->wbits == 0)
+                    state->wbits = 15;
                 state->check = crc32(0L, Z_NULL, 0);
                 CRC2(state->check, hold);
                 INITBITS();