ast.bi: Remove dead hTruncateInt() declaration
ASM backend: Adjust emitVARINIi()'s value parameter to be a LONGINT

This way the str() it does will be a str(longint) instead of a
str(integer), i.e. it will produce the same output no matter whether
on 32bit or 64bit. E.g. &hFFFFFFFF in variable initializers will now
always be emitted as 4294967295 instead of -1 (with 32bit signed Integer)
or 4294967295 (with 64bit signed Integer).

This matches the other code dealing with raw values (e.g. FBVALUE or
IR's _emitVarIniI()).
ASM backend: Combine emitVARINIi() and emitVARINI64()

Now it matches the IR interface which also only has a single emitVarIniI()
callback.
Combine symbAllocIntConst() and symbAllocLongIntConst() in similar way

The two were exactly the same except for the value parameter type which is
only used as input to the hex() call, resulting in hex(longint) in
symbAllocLongIntConst() (intended for 64bit values) and hex(integer) in
symbAllocIntConst() (intended for 32bit values).

Not only is that duplicate code, using Integer for 32bit is also suboptimal
since it changes to 64bit on 64bit. So now the combined function uses
hex(longint) and hex(long) for 64bit/32bit values respectively.