Fix 🩹 (almost) all warnings ⚠️ with default configuration (DIM=3, openMP+MPI, double precision, no advanced solvers, no QED, native output) (#1263)

This PR should fix almost all the compilation warnings in the default configuration (DIM=3, openMP+MPI, double precision, no advanced solvers, no QED, native output...). Or at least it does that on my system (my compiler is `g++ (Ubuntu 9.3.0-10ubuntu2) 9.3.0` ).

I have just two residual warnings:

### 1
```
[ 89%] Building CXX object CMakeFiles/WarpX.dir/Source/Parser/wp_parser.lex.cpp.o
wp_parser.lex.c:1356:17: warning: ‘void yyunput(int, char*)’ defined but not used [-Wunused-function]
```
I don't know if `yyunput(int, char*)` is there for a reason, even if it is not used. So I didn't do anything.


### 2
```
[ 96%] Building CXX object CMakeFiles/WarpX.dir/Source/Utils/CoarsenIO.cpp.o
/home/luca/Projects/warpx_dir/WarpX/Source/Particles/WarpXParticleContainer.cpp: In member function ‘void WarpXParticleContainer::AddNParticles(int, int, const ParticleReal*, const ParticleReal*, const ParticleReal*, const ParticleReal*, const ParticleReal*, const ParticleReal*, int, const ParticleReal*, int, int)’:
/home/luca/Projects/warpx_dir/WarpX/Source/Particles/WarpXParticleContainer.cpp:102:44: warning: unused parameter ‘nattr’ [-Wunused-parameter]
  102 |                                        int nattr, const ParticleReal* attr, int uniqueparticles, int id)
```
The first line of `AddNParticles` is `BL_ASSERT(nattr == 1); //! @fixme nattr is unused below: false sense of safety` . So I thought that there might be something to fix here and I didn't do anything.

2 files changed, 6 insertions, 1 deletions

diff --git a/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/CartesianCKCAlgorithm.H b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/CartesianCKCAlgorithm.H
index 89370c57b..f4c911db7 100644
--- a/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/CartesianCKCAlgorithm.H
+++ b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/CartesianCKCAlgorithm.H
@@ -176,6 +176,7 @@ struct CartesianCKCAlgorithm {
                       +  F(i-1,j+1,k+1,ncomp) - F(i-1,j  ,k+1,ncomp)
                       +  F(i+1,j+1,k-1,ncomp) - F(i+1,j  ,k-1,ncomp)
                        +  F(i-1,j+1,k-1,ncomp) - F(i-1,j  ,k-1,ncomp));
+        amrex::ignore_unused(n_coefs_y);
 #elif (defined WARPX_DIM_XZ)
         amrex::ignore_unused(F, coefs_y, n_coefs_y,
             i, j, k, ncomp);
@@ -198,6 +199,7 @@ struct CartesianCKCAlgorithm {
 #if defined WARPX_DIM_3D
         Real const inv_dy = coefs_y[0];
         return inv_dy*( F(i,j,k,ncomp) - F(i,j-1,k,ncomp) );
+        amrex::ignore_unused(n_coefs_y);
 #elif (defined WARPX_DIM_XZ)
         amrex::ignore_unused(F, coefs_y, n_coefs_y,
             i, j, k, ncomp);
@@ -213,7 +215,7 @@ struct CartesianCKCAlgorithm {
     AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
     static amrex::Real UpwardDz (
         amrex::Array4<amrex::Real> const& F,
-        amrex::Real const * const coefs_z, int const /*n_coefs_z*/,
+        amrex::Real const * const coefs_z, int const n_coefs_z,
         int const i, int const j, int const k, int const ncomp=0 ) {
 
         using namespace amrex;
@@ -233,6 +235,7 @@ struct CartesianCKCAlgorithm {
                       +  F(i-1,j+1,k+1,ncomp) - F(i-1,j+1,k  ,ncomp)
                       +  F(i+1,j-1,k+1,ncomp) - F(i+1,j-1,k  ,ncomp)
                       +  F(i-1,j-1,k+1,ncomp) - F(i-1,j-1,k  ,ncomp));
+        amrex::ignore_unused(n_coefs_z);
 #elif (defined WARPX_DIM_XZ)
         return alphaz * (F(i  ,j+1,k  ,ncomp) - F(i  ,j  ,k  ,ncomp))
              + betazx * (F(i+1,j+1,k  ,ncomp) - F(i+1,j  ,k  ,ncomp)
diff --git a/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/CartesianYeeAlgorithm.H b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/CartesianYeeAlgorithm.H
index a4a94c535..d8f057a70 100644
--- a/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/CartesianYeeAlgorithm.H
+++ b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/CartesianYeeAlgorithm.H
@@ -90,6 +90,7 @@ struct CartesianYeeAlgorithm {
 #if defined WARPX_DIM_3D
         Real const inv_dy = coefs_y[0];
         return inv_dy*( F(i,j+1,k,ncomp) - F(i,j,k,ncomp) );
+        amrex::ignore_unused(n_coefs_y);
 #elif (defined WARPX_DIM_XZ)
         amrex::ignore_unused(F, coefs_y, n_coefs_y,
             i, j, k, ncomp);
@@ -112,6 +113,7 @@ struct CartesianYeeAlgorithm {
 #if defined WARPX_DIM_3D
         Real const inv_dy = coefs_y[0];
         return inv_dy*( F(i,j,k,ncomp) - F(i,j-1,k,ncomp) );
+        amrex::ignore_unused(n_coefs_y);
 #elif (defined WARPX_DIM_XZ)
         amrex::ignore_unused(F, coefs_y, n_coefs_y,
             i, j, k, ncomp);