Generate zlib CRC tables in case compiled with dynamic tables.

It is possible that the zlib being used was compiled with dynamic
CRC tables, i.e. with DYNAMIC_CRC_TABLE defined. In that case, the
tables must be generated before multiple threads can be allowed to
compute CRCs. The get_crc_table() function forces that generation.

pigz.c

@@ -4343,6 +4343,9 @@ int main(int argc, char **argv) {
         if (zlib_vernum() < 0x1230)
            throw(EINVAL, "zlib version less than 1.2.3");
 
+        // create CRC table, in case zlib compiled with dynamic tables
+        get_crc_table();
+
         // process user environment variable defaults in GZIP
         opts = getenv("GZIP");
         if (opts != NULL) {