display opt: mem size labels and minor segment reporting changes

for mem size labels: add one new "BUG" entry at the start of the array
  so `mem_size` does not need to be adjusted before being used to look
  up a string from the `MEM_SIZE_STRINGS` array. it's hard to measure
  the direct benefit of this, but it shrinks codegen size by a bit and
  simplfies a bit of assembly....

for segment reporting changes: stos/scas/lods do not actually need
  special segment override logic. instead, set their use of `es` when
  decoded, if appropriate. this is potentially ambiguous; in non-64bit
  modes the sequence `26aa` would decode as `stos` with explicit `es`
  prefix. this is now identical to simply decoding `aa`, which now also
  reports that there is an explicit `es` prefix even though there is no
  prefix on tne instruction.

  on the other hand, the prefix-reported segment now more accurately
  describes the memory selector through which memory accesses will
  happen. seems ok?

1 files changed, 3 insertions, 2 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 188a37a..a7b8531 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -140,7 +140,8 @@ pub use real_mode::Arch as x86_16;
 
 mod safer_unchecked;
 
-const MEM_SIZE_STRINGS: [&'static str; 64] = [
+const MEM_SIZE_STRINGS: [&'static str; 65] = [
+    "BUG",
     "byte", "word", "BUG", "dword", "ptr", "far", "BUG", "qword",
     "BUG", "mword", "BUG", "BUG", "BUG", "BUG", "BUG", "xmmword",
     "BUG", "BUG", "BUG", "BUG", "BUG", "BUG", "BUG", "BUG",
@@ -194,7 +195,7 @@ impl MemoryAccessSize {
     /// "variable" accesses access a number of bytes dependent on the physical processor and its
     /// operating mode. this is particularly relevant for `xsave`/`xrstor`-style instructions.
     pub fn size_name(&self) -> &'static str {
-        MEM_SIZE_STRINGS[self.size as usize - 1]
+        MEM_SIZE_STRINGS[self.size as usize]
     }
 }