Refactor all source-allocations

Refactor all source-allocations by mold-allocations and assigments.

Why:

Soucer-allocation generates memory leaks that must be avoided.
Hopefully, mold-allocation/assignment should not.

Side effects:

Nothing (apparently), memory leaks occurences must still be checked.

Author: szaghi

src/lib/foodie_integrator_adams_moulton.f90

@@ -352,7 +352,8 @@ subroutine integrate(self, U, previous, Dt, t, iterations, autoupdate)
   autoupdate_ = .true. ; if (present(autoupdate)) autoupdate_ = autoupdate
   if (self%steps>0) then
     if (present(iterations)) then ! perform fixed point iterations
-      allocate(delta, source=previous(self%steps))
+      allocate(delta, mold=U)
+      delta = previous(self%steps)
       do s=0, self%steps - 1
         delta = delta + previous(s+1)%t(t=t(s+1)) * (Dt * self%b(s))
       enddo

src/lib/foodie_integrator_backward_differentiation_formula.f90

@@ -224,7 +224,8 @@ subroutine integrate(self, U, previous, Dt, t, iterations, autoupdate)
 
   autoupdate_ = .true. ; if (present(autoupdate)) autoupdate_ = autoupdate
   iterations_ = 1 ; if (present(iterations)) iterations_ = iterations
-  allocate(delta, source=previous(self%steps) * (-self%a(self%steps)))
+  allocate(delta, mold=U)
+  delta = previous(self%steps) * (-self%a(self%steps))
   do s=1, self%steps - 1
     delta = delta + previous(s) * (-self%a(s))
   enddo

src/lib/foodie_integrator_runge_kutta_embedded.f90

@@ -679,8 +679,8 @@ subroutine integrate(self, U, stage, Dt, t)
   integer(I_P)                                     :: s         !< First stages counter.
   integer(I_P)                                     :: ss        !< Second stages counter.
 
-  allocate(U1, source=U)
-  allocate(U2, source=U)
+  allocate(U1, mold=U) ; U1 = U
+  allocate(U2, mold=U) ; U2 = U
   error = 1e6
   do while(error>self%tolerance)
     ! compute stages