Add `unstd.c.string.tempCString`
Improve `unstd.c.string` module documentation.
Add reallocation functions to `unstd.memory.allocation`.

Add `unstd.memory.allocation.{reallocate,tryReallocate,rawReallocate,tryRawReallocate}`.
Don't use C's malloc/free in `weakref` module.
Don't use C's memmove in `weakref` module.