EnumResourceNames/Ex: Add remark about resource name lifetime for the callback

[MatejKafka]

The current docs do not specify if it's safe to use the returned resource name outside of the callback (e.g. storing it in a variable for later comparison). Since the whole PE module is loaded in memory, a feasible implementation could return a pointer to the string inside the mapped image, so it's not "obvious" that a single buffer is reused for all callback invocations.

From my testing, the functions reuse a single internal buffer where the resource name is copied (the pointer passed for string resource names is the same in all invocations). I'm adding a remark that describes this, and also clarifies that the callee does not need to free the pointed-to memory at the end of the callback.

[prmerger-automator]

@MatejKafka : Thanks for your contribution! The author(s) have been notified to review your proposed change.