Const-correct a LAPACK declaration and add aarch64 as a 64-bit architecture (#1859)

* Added aarch64 to list of 64-bit architechtures

* Const-corrected declaration of ssyevr

dlib/matrix/lapack/fortran_id.h

@@ -47,7 +47,7 @@ namespace dlib
     namespace lapack
     {
             // stuff from f2c used to define what exactly is an integer in fortran
-#if (defined(__alpha__) || defined(__sparc64__) || defined(__x86_64__) || defined(__ia64__)) && !defined(MATLAB_MEX_FILE) && !defined(USE_64BIT_LAPACK_INTEGERS)
+#if (defined(__alpha__) || defined(__sparc64__) || defined(__x86_64__) || defined(__ia64__) || defined(__aarch64__)) && !defined(MATLAB_MEX_FILE) && !defined(USE_64BIT_LAPACK_INTEGERS)
             typedef int integer;
             typedef unsigned int uinteger;
 #else

dlib/matrix/lapack/syevr.h

@@ -23,7 +23,7 @@ namespace dlib
                 void DLIB_FORTRAN_ID(ssyevr) (const char *jobz, const char *range, const char *uplo, const integer *n, 
                                               float *a, const integer *lda, const float *vl, const float *vu, const integer *il, 
                                               const integer *iu, const float *abstol, integer *m, float *w, 
-                                              float *z_, integer *ldz, integer *isuppz, float *work, 
+                                              float *z_, const integer *ldz, integer *isuppz, float *work, 
                                               const integer *lwork, integer *iwork, const integer *liwork, integer *info);
             }