Follow up: Modifying the "StgHeader" struct

[Adithya Kumar]

Hey folks,

I'm adding a field to "StgHeader" under a flag.

```
typedef struct {
    const StgInfoTable* info;
#if defined(NEW_WAY)
    StgWord             new_field;
#endif
#if defined(PROFILING)
    StgProfHeader         prof;
#endif
} StgHeader;

typedef struct {
    const StgInfoTable* info;
#if defined(NEW_WAY)
    StgWord             new_field;
#endif
#if defined(PROFILING)
    StgProfHeader         prof;
#endif
    StgSMPThunkHeader     smp;
} StgThunkHeader;
```

Follow-up changes:
==================

The following are the additional changes I've made following the `PROFILING`
flag:

Similar to `PROF_HDR_FIELDS` macro, I've added `NEW_HDR_FIELDS` macro:

```
#if defined(NEW_WAY)
#define NEW_HDR_FIELDS(w_,hdr) w_ hdr,
#else
#define NEW_HDR_FIELDS(w_,hdr) /* Nothing */
#endif
```
and updated the required stg code accordingly following the changes from
`PROF_HDR_FIELDS`.

I've also updated `GHC.Exts.Heap.ClosureTypes.closureTypeHeaderSize`
accordingly.

Error:
======

I'm greeted with the following error,
```
ASSERTION FAILED: file rts/StgStartup.cmm, line 100
```

Basically, the following assert fails
```
#define CHECK_SENSIBLE_REGS()                           \
    ASSERT(Hp != 0);                                    \
    ASSERT(HpAlloc == 0);                               \
    ASSERT(Sp != 0);                                    \
    ASSERT(SpLim != 0);                                 \
    ASSERT(SpLim - WDS(RESERVED_STACK_WORDS) <= Sp);
```

More context for the error:
===========================

Values for the correct version:
```
Hp      283468906488
HpAlloc 0
Sp      283468911440
SpLim   283468910784
SpLim - WDS(RESERVED_STACK_WORDS) 1069080
```

Values with the changes:
```
Hp      283468906488
HpAlloc 0
Sp      7532120
SpLim   9301536
SpLim - WDS(RESERVED_STACK_WORDS) 9301368
```

I recorded these values by calling a C print from the Cmm code.

Clearly, my changes messed up a lot of things. How do I go about this now?
The
past 2 weeks I've only been looking at a lot of ghc code. If any more
additional
context is required I can provide it.

Best,
Adithya
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