Allocator may return misaligned pointers on 32b platforms

[boguscoder]

This was caught by UBSAN (exact repro is project specific but if required I can try building a clean one)

The gist is that runtime error: constructor call on misaligned address 0xeefae004 for type 'Luau::AstExprConstantNumber', which requires 8 byte alignment

while Allocator attempts to do some alignment, its not doing anything explicitly when allocating new pages. on 32bit platform this leads to whole Page being OK-aligned but since we are returning page->data its 4 bytes offsetted and is not 8 byte aligned anymore

One of the solutions is just to add alignas(8) to data member in Page type