Modifications to support MSVC compiler

[purpledawn777]

Hello, fyi the following modifications need to be made to support microsoft's compiler (srand48,drand48 and c99 dynamic arrays not supported):
core/_ext/src_numerics.c
add this below the #includes:
#ifdef _MSC_VER
#define srand48(x) srand((x))
#define drand48() (rand()/(RAND_MAX + 1.0))
#endif

funcnet/_ext/src_numerics.c
in _get_nearest_neighbors_fast,
change:
int i, j, index=0, t, m, n, d, kxz, kyz, kz, indexfound[T];
double dz=0., dxyz=0., dx=0., dy=0., eps, epsmax;
double dist[Tdim], dxyzarray[k+1];
to:
int i, j, index=0, t, m, n, d, kxz, kyz, kz;
int indexfound = (int*) malloc(sizeof(int)T);
double dz=0., dxyz=0., dx=0., dy=0., eps, epsmax;
double dist = (double*)malloc(sizeof(double)Tdim);
double* dxyzarray = (double*) malloc(sizeof(double)*(k+1));

and add to the end of the method:
free(dist);
free(dxyzarray);
free(indexfound);

[ntfrgl]

Thank you for your contribution, @purpledawn777! The commit above adopts a similar approach, although it uses Cython for the functions requiring random numbers and alloca instead of malloc/free.