patch to mips16 truncdi{h,q}i2

[Jeffrey A Law]

  In message < m0y2H5D-0006vBC@cetus.cygnus.com >you write:
  > 
  > For the 4100 -mips16, the following bit of code causes gcc
  > to recur in convert_move until it runs out of stack; similar
  > code useing a long and a char will also cause this.  The
  > following patch defines a mips16 version of of truncdihi2
  > and truncdiqi2.
Actually, wait, I don't see any "double" shift instructions in 
my mips16 info....

jeff