Document how to get a development version of wxMaxima on macOS

On macOS, the current version of wxMaxima is now supported by MacPorts. https://www.macports.org/

[1] So you can get the version 18.02.0 with the next command:

$ sudo port install wxmaxima

[2] If you want to try a development version of wxMaxima, run the next command:

$ sudo port install wxmaxima-devel

Note: If you have already installed wxMaxima-18.02.0, you must deactivate it with the next command before installing the development version:

$ sudo port deactivate wxmaxima

Note: If you want to use wxWidgets-3.1.1 instead of 3.0.4, then add the "+wx32" variant as follows:

$ sudo port install wxmaxima-devel +wx32

Note: wxMaxima.app is installed to the "/Applications/MacPorts/" directory.

[3] If you want to try the latest development version of wxMaxima, you can do as follows:

(1) You have to get the commit hash which refers to the development version of wxMaxima. (see https://github.com/andrejv/wxmaxima/commits/master) e.g. assuming that you choose the hash '1f86a895286f5e43636dd8e4149ab3e3fc3ec26c'.

(2) Open the 'Portfile' file of wxMaxima with the next command in order to change the commit hash:

$ sudo nano `port dir wxmaxima`/Portfile

(3) Find the hash 'b32fed0d535c05d589d1f573d2c0f4f839180d18' and change it to '1f86a895286f5e43636dd8e4149ab3e3fc3ec26c'. e.g. you can find the following line:

github.setup    andrejv wxmaxima b32fed0d535c05d589d1f573d2c0f4f839180d18

(4) After saving the modified 'Portfile', verify the checksums with the next command:

$ sudo port -v checksum wxmaxima-devel

Then the result message is displayed.

(5) Find the "The correct checksum line may be:" lines to get the correct checksums.(rmd160, sha256, and size) e.g. you can find the following lines: 

The correct checksum line may be:
checksums           rmd160  282fed8fe6757d4a39d73a8c5fc76d6126891b9f \
                    sha256  9c8af280b4f5dfd745cff5d1e29a832c9adabe98bf4486aca8ed0bd305177c9f \
                    size    12011303

(6) Open the 'Portfile' file of wxMaxima with the next command in order to change the checksums and version:

$ sudo nano `port dir wxmaxima`/Portfile

(7) Find the following checksum lines and change them to the correct checksums. e.g. you can find the following lines:

github.setup    andrejv wxmaxima 1f86a895286f5e43636dd8e4149ab3e3fc3ec26c
checksums       rmd160  86fcf85ddae42e84884a708d55acff393152ed23 \
                sha256  e34256294c51a37d80947b92d3cd979456bf0c8ae53a21ce6cbab63d99143bf2 \
                size    12739940
version         18.02-dev-20180616

(8) Find the string "18.02-dev-20180616" of the version line and change it to "18.02-dev-20180704".

(9) After saving the modified 'Portfile', install 'wxmaxima-devel' with the next command:

$ sudo port install wxmaxima-devel +wx32

Then the development version of wxMaxima is installed to the "/Applications/MacPorts/" directory.

wxMaxima-developers / wxmaxima

Document how to get a development version of wxMaxima on macOS #1014