The Read Composed Line routine reads a line of input composed of
    normal keystrokes and equivalence strings.

    Format

      SMG$READ_COMPOSED_LINE  keyboard-id [,key-table-id]

                              ,resultant-string [,prompt-string]

                              [,resultant-length] [,display-id]

                              [,flags] [,initial-string]

                              [,timeout] [,rendition-set]

                              [,rendition-complement]

                              [,word-terminator-code]