Implement linearRealloc

[BallM4788]

linearAlloc() was declared but never implemented. @WinterMute anything I'm missing or needs to be fixed?

Nitty gritty:

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Reallocates a buffer by shrinking or growing the size listed in the associated MemChunk, and appropriately growing or shrinking the size listed in the MemBlock associated with the adjacent unallocated memory.

• linearRealloc() will adjust the requested size to comply with the buffer's linear mask. A new member linearMask has been added to the memChunk struct to facilitate this. If the adjusted size is identical to the MemChunk's existing size, no modification is done.
• If shrinking the buffer results in a section of unallocated memory where none existed prior, a new MemBlock will be appropriately inserted into the linear pool.
• When growing the buffer, the initially-mentioned MemBlock will be deleted if its resulting size is 0. If the adjacent unallocated memory section is insufficient for expanding the buffer, linearRealloc() will:
  1. Attempt to allocate a new buffer of the desired size. Continue with the following steps if successful.
  2. Copy the contents of the original buffer into the new buffer.
  3. Deallocate the original buffer.

In successful cases, LinearAlloc() will return a pointer to the reallocated memory. If reallocation fails at any point, no changes are made and a null pointer is returned.

[BallM4788]

@WinterMute Would you mind checking this out?