Remove USHORT typedef.

[waywardmonkeys]

This was defined as unsigned for DOS and unsigned short for everyone else, but it was only used in bitfield definitions where just having unsigned is fine.

Other bitfield definitions (in some cases, immediately adjacent to the ones modified here), were already just using a bare unsigned, so this improves the consistency of the definitions.

[waywardmonkeys]

There's a reasonable argument to be made that any bitfield that is just 1 bit could instead be a _Bool / bool, but that'd be for some other PR, not just cleaning up USHORT.

[nbriggs]

I believe these (all?) need to be "unsigned short" rather than "unsigned" because structures will be pointing to 16-bit word(s) shared with the Lisp code and have to be bit/size exact.

[waywardmonkeys]

These are the storage types within the structs, which have specific bit sizes assigned to them. The type here only ends up mattering for what happens when a value is extracted from the struct ... and for whether it is signed or unsigned.

Also note that a number of other structs are using bare unsigned as well.

[nbriggs]

Clang and GCC seem to be consistent in the way they lay out the bits, but as far as I recall there was no requirement that pad bits be in any particular place when the number of bits didn't add up to the size of the field, and the alignment requirement is that of the largest element of the struct.

With reference to this source:

int main(int argc, char *argv[])
{
struct uswbits {
  unsigned short a:1;
  unsigned short b:7;
  unsigned short c:8;
} us ;

struct uwbits {
  unsigned a:1;
  unsigned b:7;
  unsigned c:8;
} u;
 us.a = u.a;
}

% clang -cc1 -fdump-record-layouts /tmp/foo2.c

*** Dumping AST Record Layout
         0 | struct uwbits
     0:0-0 |   unsigned int a
     0:1-7 |   unsigned int b
     1:0-7 |   unsigned int c
           | [sizeof=4, align=4]

*** Dumping AST Record Layout
         0 | struct uswbits
     0:0-0 |   unsigned short a
     0:1-7 |   unsigned short b
     1:0-7 |   unsigned short c
           | [sizeof=2, align=2]

The structs that use bare unsigned should have bit fields that add up to 32. Some of the structs are going to be used as templates over a 16-bit aligned pointers, some over a 32-bit aligned pointers, and I'd rather not introduce unnecessary warnings for alignment mismatches when it's trivial to get it right.