Libs: Drop useless -Wsign-conversion.
Libs: Drop useless -Wsign-conversion.

bwipp/postscriptbarcode,bwipp/postscriptbarcode,bwipp/postscriptbarcode,bwipp/postscriptbarcode,bwipp/postscriptbarcode,bwipp/postscriptbarcode,bwipp/postscriptbarcode,bwipp/postscriptbarcode