Ignores book number when sorting pages

[kwilson7770]

This tool ignores book numbers when creating the index sorted by page numbers. There are the two lines in the main.idx file being used.

\indexentry{This is a test|book{1}}{34}
\indexentry{This is a test|book{3}}{33}

This generates:

This is a test . . . . . . . . . . . . . . . . . . . . . . 123.3–33, 123.1–34

Instead of

This is a test . . . . . . . . . . . . . . . . . . . . . . 123.1–34, 123.3–33