Get rid of src/lib/common/land.c

There are several files with land unit subroutines.  This one is in an
awkward place: it depends on stuff from ../subs, which contributes to
libcommon.a's ugly dependencies.  Move its contents to logical places
(use internal linkage where possible), and remove it.

src/lib/subs/list.c

@@ -39,9 +39,11 @@
 #include "misc.h"
 #include "nat.h"
 #include "nsc.h"
+#include "path.h"
 #include "plane.h"
 #include "player.h"
 #include "prototypes.h"
+#include "sect.h"
 #include "ship.h"
 #include "xy.h"
 
@@ -271,6 +273,42 @@ num_shipsatxy(coord x, coord y, int wantflags, int nowantflags)
     return ships;
 }
 
+int
+adj_units(coord x, coord y, natid own)
+{
+    int i;
+    struct sctstr sect;
+
+    for (i = DIR_FIRST; i <= DIR_LAST; i++) {
+	getsect(x + diroff[i][0], y + diroff[i][1], &sect);
+	if (has_units(sect.sct_x, sect.sct_y, own, 0))
+	    return 1;
+    }
+    return 0;
+}
+
+int
+has_units(coord x, coord y, natid cn, struct lndstr *lp)
+{
+    int n;
+    struct lndstr land;
+
+    for (n = 0; ef_read(EF_LAND, n, &land); n++) {
+	if (land.lnd_x != x || land.lnd_y != y)
+	    continue;
+	if (lp) {
+	    /* Check this unit.  If it is this one, we don't want
+	       it included in the count. */
+	    if (lp->lnd_uid == land.lnd_uid)
+		continue;
+	}
+	if (land.lnd_own == cn)
+	    return 1;
+    }
+
+    return 0;
+}
+
 /*
  * is p a list of ships/planes/units?
  */

src/lib/subs/lndsub.c

@@ -53,6 +53,7 @@
 
 static void lnd_mess(char *, struct ulist *);
 static int lnd_hit_mine(struct lndstr *, struct lchrstr *);
+static int has_helpful_engineer(coord, coord, natid);
 
 double
 attack_val(int combat_mode, struct lndstr *lp)
@@ -1248,6 +1249,26 @@ lnd_fortify(struct lndstr *lp, int mob)
     return hard_amt;
 }
 
+/*
+ * Is there a engineer unit at X,Y that can help nation CN?
+ */
+static int
+has_helpful_engineer(coord x, coord y, natid cn)
+{
+    struct nstr_item ni;
+    struct lndstr land;
+
+    snxtitem_xy(&ni, EF_LAND, x, y);
+    while (nxtitem(&ni, &land)) {
+	if (land.lnd_own != cn && getrel(getnatp(land.lnd_own), cn) != ALLIED)
+	    continue;
+	if (lchr[(int)land.lnd_type].l_flags & L_ENGINEER)
+	    return 1;
+    }
+
+    return 0;
+}
+
 /*
  * Set LP's tech to TLEV along with everything else that depends on it.
  */