Lagrangian mechanics system simulation in C

Examples:

• Double Pendulum
• TODO: Add more examples
• TODO: Implement constraints
• TODO: Add GIF here

Dependencies:

• SymEngine
  • may depend on GMP, MPFR
• LLVM for SymEngine's Just-in-Time compilation for numerical evaluation
  • ensure SymEngine is compiled against LLVM, seems to perform ~10x on my machine with this
• libm/<math.h>
• A terminal that supports ANSI escape codes and tcsetattr