Add realloc function to jmem

[mmatyas]

This patch extends jmem functionality by adding a realloc function.
This opens up other paths of optimization which can result in smaller
peak memory usage and faster execution times, due to not having to
duplicate memory when we need to extend blocks.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai [email protected]

[mmatyas]

The feature this patch implements will be used for the string construction buffer optimizations -- see #2617.

[akosthekiss]

PR author and commit author are quite different. Interestingly, CI is not unhappy about that. Should this get approved and landed (via squash&merge on the web interface), I'm not completely sure what will happen. If I recall correctly, GH will rewrite at least the committer (making it the person who has pushed the green button). Whether the author gets also rewritten, I'm not sure. But either @mmatyas or @dbatyai will lose credit. Just sayin'.

[DanielBallaSZTE]

As far as I know the last line of the commit should be the sign-off with the author of the commit.
A good feature to use in this case is the co-author feature.
You can read more about it here:
https://help.github.com/articles/creating-a-commit-with-multiple-authors/

[akosthekiss]

@DanielBallaSZTE That looks like a nice feature. Does it work with our DCO signoff requirement? (It must be the last line of the commit message. Github co-author markups must also be on the last line(s) of the commit message. Do these conflict?)

[DanielBallaSZTE]

@akosthekiss
I used it several times, and put it right before the sign-off message. It didn't conflict, and marked @rerobika as the co-author in the commit.
(Reference: #2514)

[zherczeg]

How this is compatible with system allocator? I am not sure all embedded systems has realloc.

[akosthekiss]

@DanielBallaSZTE I cannot find the referenced commit among @rerobika 's contributions.