[GRASS5] Sites 5.1/7

[Radim Blazek]

I have modified G_site* functions to use vectors. It is temporary solution how to
update s.* modules to 5.1/7 v.* wihout a lot of work. Attributes are supported by
G_site_get() but G_site_put() writes CELL category only (attributes may be added later
if needed). Old G_site* functions used by v.in.sites are renamed to G_oldsites*.
There are only 2 s.* modules in 5.1/7 (s.in.ascii,s.out.ascii; to be removed later) 
for tests of new SITESLIB. I updated 2 other modules, v.random and v.surf.idw.
It is not my intention to update all other s.* modules as mostly I don't know
too much about them and don't need them. To updated s.* to v.*, it is typicaly necessary:
1) ->key = "sites"  =>  "input" / "output" / "vector"
2) ->description="... sites ..." => "... vector ..."
3) G_find_file ("site_lists",,) => G_find_sites (,)
4) fclose() => G_sites_close()

New version is slower (dbf driver, 10000 points): 
                 time(200x200cells)   time(667x667cells)
s.surf.idw              0.43                10.71
v.surf.idw              1.76                11.35

Radim