Update ExprTk to 0.0.3 on release branch

[ArashPartow]

Change to point to the release branch which will always be stable and verified/tested.

[end2endzone]

I'll check why Appveyor is failing. Probably not your fault. Thanks for creating an official tag. Indeed, I did not liked having to link to a specific commit.

[end2endzone]

There is still a reference to the "old" directory exprtk-master which comes from extracting the library in .zip file. It is located in file src/libexprtk/CMakeLists.txt#L19. I think the easiest solution is to proceed with the rename of exprtk-master to exprtk-0.0.3 in the file mentioned above. This will fix the missing include directory [PROJECT_DIR]\build\external\exprtk-0.0.3.

If you could also change this, I think the PR would be complete and would pass all checks. I would gladly accept the PR. I am still new with the collaboration workflow and I do not know if I could "add" this modification on top of your PR.

I will have to fix this eventually. I am compiling with Visual Studio 2019. This project is a DLL which wraps your lib. I cannot simply use your makefile because I must add new compilation flags (more specifically /bigobj) to be able to compile the library.

On a side note, it is a very nice gesture to trace back people that uses your library and notify them about your latest release. I am now watching your repo for new releases.

[ArashPartow]

@end2endzone I also did a minor clean-up as part of your suggested fix, so for the next tag release the diff should now only be one line.

wrt Makefile, there is a CMake branch, with associated release branch tags (eg: 0.0.3-cmake) which should greatly simply the ExprTk related CMake incantations in ShellAnything: https://github.com/ArashPartow/exprtk/tree/cmake

CMake recipe exprtk.cmake:

if(TARGET exprtk::exprtk)
    return()
endif()

message(STATUS "Third-party: creating target 'exprtk::exprtk'")

include(FetchContent)

FetchContent_Declare(
    exprtk
    GIT_REPOSITORY https://github.com/arashpartow/exprtk.git
    GIT_TAG 0.0.3-cmake
)

FetchContent_MakeAvailable(exprtk)

Note: For some reason github says "We don’t support that file type.", so I couldn't attach it.