fix bessel algo errors, add test framework

Fixed bad computations in all bessel functions

Added Python test framework that can test any function (PR welcomed for more complete calc function coverage).

bugfixes

a wrapup release for past year of bugfixes

add CDash

one-step cmake build

improve build options, cleanup unneeded options

v1.2.0

ci: meson exe for distro

Cleanup CI, add AppVeyor artifact

• cleanup CI and build, assume error stop is available
• add AppVeyor build of Windows rpncalc.exe artifact

best practices

• Functionalize, deduplicate
• use standard separate .f files from Netlib, especially for Bessel, rather than jamming everything into a huge file
• add jinc(), J'1()
• use associate to make code neater

Registers and robustness

• The registers were broken, probably since inception. Now they work, all ten of them
• increased test coverage of functions and of the CLI via a test text file
• included basic help command

arbitrary stack size--at runtime

Exploit key Fortran feature of arbitrary sized arrays at runtime to set the stack size with command line option by end user.

e.g.

rpncalc 25

makes stack size 25. Default is 4.

Modularize, modernize

Increase ease of adding/modifiying/using functions in other programs and this one by modularizing the functions into distinct files / modules.

Regex'd massive if/else tree to select case

updated Fortran 77 stack-handling code to Fortran 95

Polymorphism, fixed command line

Some functions are polymorphic, to demonstrate the ease of doing so via module interface statements--see the top of funcs.f90.

The command line was not allowing multiple numbers on one line, this is fixed.