Couchdb-couch_set_view-19-compaction-retry test failure for s390x

The "if (fscanf(stdin, "%c\n", (char *)&view_file_type) != 1)" gets wrong input character if we don't do this change. The C and C++ standards allows the character type char to be signed or unsigned, depending on the platform and compiler. For s390x, the type of char is unsigned. This variation causes getting junk characters for s390x. The code change will make the type consistent across all platforms. Please find attached file for the code diff.