[C API] PR19859: Add LLVMGetFCmpPredicate and LLVMConstRealGetDouble.

Patch by Gabriel Radanne <drupyog@zoho.com>.
[OCaml] PR19859: Add Llvm.{fcmp_predicate,float_of_const}.

Patch by Gabriel Radanne <drupyog@zoho.com>.
[OCaml] PR19859: Add tests for reading the values of numeric constants.

Patch by Gabriel Radanne <drupyog@zoho.com>.
[C API] PR19859: Add functions to query and modify branches.

Patch by Gabriel Radanne <drupyog@zoho.com>.
[OCaml] PR19859: Add functions to query and modify branches.

Patch by Gabriel Radanne <drupyog@zoho.com>.