ARC options documentation questions

[Sandra Loosemore]

I noticed a bunch of copy-editing issues in the "ARC Options" section of 
invoke.texi.  I'm willing to take a stab at fixing them, but I need some 
technical assistance since I'm not familiar with the details of this 
architecture myself.

* In e.g. "Compile for ARC 600 cpu with norm instruction enabled." is 
"norm" literally the name of an instruction, GCC implementor jargon, or 
a term that is used and capitalized like that in the processor 
documentation?  Ditto for "mul32x16", "mul64", "LR", "SR", "mpy", "mac", 
"mulu64", "swap", "DIV/REM", "MPY", "MPYU", "MPYW", "MPYUW", "MPY_S", 
"MPYM", "MPYMU".  For other targets, literal names of instructions are 
usually marked up with @code{}, and it would be good to be consistent 
about whether uppercase or lowercase is preferred for ARC instruction 
names.  If any of these are GCC-specific internal jargon, it would be 
better to use the same terminology that appears in the processor 
documentation, or failing that, real English words.

* In "FPX: Generate Double Precision FPX instructions", is "Double 
Precision FPX" a proper name literally capitalized like that, or is this 
a mistake for "double-precision FPX instructions"?  Likewise for "Single 
Precision FPX"?

* In e.g. the discussion of fpuda_div, is "simple precision" a typo for 
"single precision"?  Likewise is "multiple and add" a typo for "multiply 
and add"?

-Sandra