Fix the problems exposed by the callingconv1.d test case. The first was that unless otherwise specified, inputs are assumed to be in registers even if they specify a "matching output" that's in memory. While testing that fix, I also ran into a bug causing the generated "matching output" for any input was always the first one instead of the correct one.

#ifndef LDC_GEN_AA_H
#define LDC_GEN_AA_H

DValue* DtoAAIndex(Loc& loc, Type* type, DValue* aa, DValue* key, bool lvalue);
DValue* DtoAAIn(Loc& loc, Type* type, DValue* aa, DValue* key);
void DtoAARemove(Loc& loc, DValue* aa, DValue* key);

#endif // LDC_GEN_AA_H