Make easings.h use powf and sqrtf instead of pow and sqrt.

* Update year of copyright notices

* Fix mistake in comment

* Fix typo ("algorythms")

* Replace tabs with spaces

* Remove trailing whitespace and fix mistake in comment

* Fix ExportImageAsCode missing comment rectangle corner

* Replace tab with spaces

* Replace tabs with spaces

Variable operations inside the functions should be evaluated before the function operations.

Added guards to not redefine it if the user is using it with raylib.h
also added an 'f' at the end of the define to keep compliant with raylib's PI define

PI is not always defined in math.h, thus it must be defined in this header