1)  In 5.0, I think I just didn't include lparser.c and that removed the 
parser (it's been a while).  How do I do that in 5.1?
   
Same as in 5.0: compile etc/noparser.c and add it to your project or list
of objects in a Makefile. No need to change the core library. The linker will
be happy to use what is in etc/noparser.c if it comes before the core library.
 
2)  In trying to test out 5.1 in my application, I got a lockup.  I was 
doing a:
   if ( luaL_loadbuffer(L,B,1069,"'..Main..'") || lua_pcall(L,0,0,0) )
       fprintf(stderr,"%s\n",lua_tostring(L,-1));
   
Are you sure that there are 1069 bytes in B?
 
   However, the buffer I was passing it was compiled with Lua 5.0.  Did 
any opcodes change between 5.0 and 5.1?
   
Yes, but like Asko said, you should have got an error message.
I think you have read beyond whatever B has. But I'm surprised you didn't
get an error message.
--lhf