simplify foreigncall handling

[KristofferC]

Instead of reconstructing the surface syntax we can just pass along the arguments to a Expr(:foreigncall, ...).

Fixes #552

[codecov]

Codecov Report

Merging #554 (87c7c07) into master (39d04c7) will decrease coverage by 0.53%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #554      +/-   ##
==========================================
- Coverage   86.80%   86.26%   -0.54%     
==========================================
  Files          12       12              
  Lines        2539     2505      -34     
==========================================
- Hits         2204     2161      -43     
- Misses        335      344       +9     

Impacted Files	Coverage Δ
src/optimize.jl	93.93% <100.00%> (-3.65%)	⬇️
src/utils.jl	88.60% <0.00%> (+0.21%)	⬆️

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[Keno]

Fixes #552, hopefully

[KristofferC]

Some of the code needs to be put back to handle e.g. the

function add1234(x::Tuple{Int32,Int32,Int32,Int32})
    Base.llvmcall("""%3 = extractvalue [4 x i32] %0, 0
      %4 = extractvalue [4 x i32] %0, 1
      %5 = extractvalue [4 x i32] %0, 2
      %6 = extractvalue [4 x i32] %0, 3
      %7 = extractvalue [4 x i32] %1, 0
      %8 = extractvalue [4 x i32] %1, 1
      %9 = extractvalue [4 x i32] %1, 2
      %10 = extractvalue [4 x i32] %1, 3
      %11 = add i32 %3, %7
      %12 = add i32 %4, %8
      %13 = add i32 %5, %9
      %14 = add i32 %6, %10
      %15 = insertvalue [4 x i32] undef, i32 %11, 0
      %16 = insertvalue [4 x i32] %15, i32 %12, 1
      %17 = insertvalue [4 x i32] %16, i32 %13, 2
      %18 = insertvalue [4 x i32] %17, i32 %14, 3
      ret [4 x i32] %18""",a,
      Tuple{Tuple{Int32,Int32,Int32,Int32},Tuple{Int32,Int32,Int32,Int32}},
        (Int32(1),Int32(2),Int32(3),Int32(4)),
        x)
end
@test @interpret(add1234(map(Int32,(2,3,4,5)))) === map(Int32,(3,5,7,9))

case

[aviatesk]

The failures in nightly CI are known and unrelated. Thanks so much for working on this!