Proper fixedpoint multiplication with precision 30 bits.

See for details http://sourceforge.net/p/cmusphinx/bugs/397



git-svn-id: svn+ssh://svn.code.sf.net/p/cmusphinx/code/trunk/sphinxbase@12567 94700074-3cef-4d97-a70e-9c8c206c02f5