MEX files: use default member initialization when possible

Automatically detected by clang-tidy with modernize-use-default-member-init
check.

mex/sources/libkorder/sylv/GeneralMatrix.hh

@@ -582,15 +582,14 @@ protected:
   // Orthogonal matrix Vᵀ
   GeneralMatrix VT;
   // Convered flag
-  bool conv;
+  bool conv {false};
 
 public:
   SVDDecomp(const GeneralMatrix& A) :
       minmn(std::min<int>(A.nrows(), A.ncols())),
       sigma(minmn),
       U(A.nrows(), A.nrows()),
-      VT(A.ncols(), A.ncols()),
-      conv(false)
+      VT(A.ncols(), A.ncols())
   {
     construct(A);
   }

mex/sources/libkorder/tl/sparse_tensor.hh

@@ -73,11 +73,10 @@ protected:
   int nr;
   int nc;
   int first_nz_row;
-  int last_nz_row;
+  int last_nz_row {-1};
 
 public:
-  SparseTensor(int d, int nnr, int nnc) :
-      dim(d), nr(nnr), nc(nnc), first_nz_row(nr), last_nz_row(-1)
+  SparseTensor(int d, int nnr, int nnc) : dim(d), nr(nnr), nc(nnc), first_nz_row(nr)
   {
   }
   virtual ~SparseTensor() = default;