add memory function accessors

[goatshriek]

While stumpless currently provides a way to control the functions used to manage dynamic memory, it does not provide matching functions to retrieve the current settings. This may be useful to library users, and would also make some of the testing code cleaner as well.

General Approach

There are a few details left out of the following outline, for you to fill in as you encounter them. If you find you need help, please ask here or on the project gitter and someone can help you get past the stumbling block.

First, read this section of the development documentation on adding new functions. Once you understand how this process works, you'll be ready to define the new functions.

Add your three new functions to include/stumpless/memory.h and the corresponding source file. You should also add tests for your new functions in test/function/memory.cpp.

Finally, update the memory counting macros used in benchmark tests to use your new functions. These are defined in include/test/helper/memory_counter.hpp. They currently assume that the settings to restore are the standard library functions, but this may not always be the case. Change the INIT_MEMORY_COUNTER macro to use your new functions instead of making this assumption.

[tertyshnyi]

Hi, I'd like to do this task. Can you assign it to me?

[goatshriek]

Sure, good luck!

[tertyshnyi]

Can you help explain what the problem might be?

[goatshriek]

What is the problem? The screenshot seems to simply show the entry example running.

[tertyshnyi]

Thank you for answering. If that's the way it's supposed to be, then I'll get to the task at hand.

[goatshriek]

Closed by #468.