Review code regarding write and the like unsuccessful because interrupted by a signal

[jnpkrn]

E.g., lib/ringbuffer.c:

748 ssize_t                                                                       
749 qb_rb_write_to_file(struct qb_ringbuffer_s * rb, int32_t fd)                  
750 {                                                                             
[...]
760                                                                               
761         /*                                                                    
762          * 1. word_size                                                       
763          */                                                                   
764         result = write(fd, &rb->shared_hdr->word_size, sizeof(uint32_t));     
765         if (result != sizeof(uint32_t)) {                                     
766                 return -errno;                                                
767         }                                                                     
768         written_size += result;                                               

It should be decided for cases when errno == EINTR whether:

• function should retry autonomously
• callsites (if any) still within libqb boundary should retry
• user's code should retry (requires this possibility documented
  properly at the respective libqb functions)