Cppcheck fixes

user_context and private are assigned twice by this same value

*q && *q != '_' check is useless since it may be written short like *q != '_' but basing on logic should be checked if q is null pointer or not

xc is used as index, but is checking after using, linebuf[xc] may be out of bounds

i index may have value 362 which will cause out of bounds array access