rs6000: New attributes for load/store: "sign_extend", "update" and "indexed"

rs6000: New attributes for load/store: "sign_extend", "update" and "indexed"

The new attributes replace the instruction types *_ext*, *_u, *_ux.

This simplifies all code that does not care about the addressing modes,
putting the burden on the code that does care (mostly the scheduling
descriptions for certain CPUs).

It fixes a few minor bugs in the process.

The "update" and "indexed" attributes are automatic for any insn that
has a MEM as operand 0 or 1.  Other insns have to set it manually, if
they do not like the default (which is "no").  Insns that are type
load/store/fpload/fpstore but have fewer than two operands need to set
it too, or the compiler will crash.  There are very few of those.

This tries not to change semantics anywhere; in particular, the string
and multiple instructions set both "update" and "indexed" (although
they are neither).

From-SVN: r210190