Fixed spelling / typos (from PowerDNS:codespell)
diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
index eae15e0..c4680a7 100644
--- a/include/polarssl/bignum.h
+++ b/include/polarssl/bignum.h
@@ -436,7 +436,7 @@
int mpi_add_abs( mpi *X, const mpi *A, const mpi *B );
/**
- * \brief Unsigned substraction: X = |A| - |B|
+ * \brief Unsigned subtraction: X = |A| - |B|
*
* \param X Destination MPI
* \param A Left-hand MPI
@@ -460,7 +460,7 @@
int mpi_add_mpi( mpi *X, const mpi *A, const mpi *B );
/**
- * \brief Signed substraction: X = A - B
+ * \brief Signed subtraction: X = A - B
*
* \param X Destination MPI
* \param A Left-hand MPI
@@ -484,7 +484,7 @@
int mpi_add_int( mpi *X, const mpi *A, t_sint b );
/**
- * \brief Signed substraction: X = A - b
+ * \brief Signed subtraction: X = A - b
*
* \param X Destination MPI
* \param A Left-hand MPI