updated for version 7.4.025
Problem:    Reading before start of a string.
Solution:   Do not call mb_ptr_back() at start of a string. (Dominique Pelle)
Added tag v7-4-025 for changeset 9085d32d7424
updated for version 7.4.026
Problem:    Clang warning for int shift overflow.
Solution:   Use unsigned and cast back to int. (Dominique Pelle)
Added tag v7-4-026 for changeset 6bbb2ae990c9