| Function silc_buffer_pull_tail
 
 SYNOPSIS
 
    static inline
    unsigned char *silc_buffer_pull_tail(SilcBuffer sb, SilcUInt32 len);
DESCRIPTION
    Pulls current tail section towards end. Length of the current valid
    data area is also incremented. Returns a pointer to the data area
    before pulling. Returns NULL on error.
EXAMPLE
    ---------------------------------
    | head  | data       | tail     |
    ---------------------------------
                         ^
                         Pulls the start of the tail section.
    ---------------------------------
    | head  | data           | tail |
    ---------------------------------
                         ^
    silc_buffer_pull_tail(sb, 23);
 
 
 
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