autodoc and examples for str2num improvement

Author: jalvesz

doc/specs/stdlib_str2num.md

@@ -35,16 +35,7 @@ Return a scalar of numerical type (i.e., `integer`, or `real`).
 ### Example
 
 ```fortran
-program example_string_to_number
-  use stdlib_kinds, only: dp
-  use stdlib_str2num, only: to_num
-  implicit none
-  character(:), allocatable :: txt
-  real(dp) :: x
-
-  txt = ' 8.8541878128e−12 '
-  x = to_num( txt , x )
-end program example_string_to_number
+{!example/strings/example_string_to_number.f90!}
 ```
 
 ## `to_num_p` - conversion of a stream of values in a string to numbers
@@ -74,20 +65,7 @@ Return a scalar of numerical type (i.e., `integer` or `real`).
 ### Example
 
 ```fortran
-program example_to_num_p
-    use stdlib_kinds, only: dp
-    use stdlib_str2num, only: to_num_p
-    character(:), allocatable, target :: chain
-    character(len=:), pointer :: cptr
-    real(dp) :: r(6)
-    integer :: i 
-
-    chain = " 1.234   1.E1 1e0     0.1234E0  12.21e+001 -34.5E1"
-    cptr => chain
-    do i = 1, 6
-        r(i) = to_num_p( cptr , r(i) ) !> the cptr pointer is shifted within the function
-    end do
-end program example_to_num_p
+{!example/strings/example_stream_of_strings_to_numbers.f90!}
 ```
 
 ## Note

example/strings/example_str2num.f90 renamed to example/strings/example_stream_of_strings_to_numbers.f90

@@ -1,4 +1,4 @@
-program example_str2num
+program example_stream_of_strings_to_numbers
     use stdlib_kinds, only: dp
     use stdlib_str2num, only: to_num_p
     character(:), allocatable, target :: chain
@@ -14,9 +14,9 @@ program example_str2num
         r(i) = to_num_p( cptr , r(i) ) !> the pointer is shifted within the function
     end do
     read(chain,*) p
-    print *, "Reading with to_num"
+    print *, "Reading with to_num_p"
     print *, r
     print *, "Reading with formatted read"
     print *, p
 
-end program
+end program example_stream_of_strings_to_numbers

example/strings/example_string_to_number.f90

@@ -0,0 +1,10 @@
+program example_string_to_number
+    use stdlib_kinds, only: dp
+    use stdlib_str2num, only: to_num
+    implicit none
+    character(:), allocatable :: txt
+    real(dp) :: x
+  
+    txt = ' 8.8541878128e−12 '
+    x = to_num( txt , x )
+  end program example_string_to_number