Put back the great_circle files in the examples/not_in_docs

docs/examples/not_in_docs/great_circle/c1.pyx

+import math
+
+def great_circle(lon1, lat1, lon2, lat2):
+    radius = 3956 # miles
+    x = math.pi/180.0
+
+    a = (90.0 - lat1)*x
+    b = (90.0 - lat2)*x
+    theta = (lon2 - lon1)*x
+    c = math.acos(math.cos(a)*math.cos(b) + math.sin(a)*math.sin(b)*math.cos(theta))
+
+    return radius*c

docs/examples/not_in_docs/great_circle/c2.pyx

+import math
+
+def great_circle(double lon1, double lat1, double lon2, double lat2):
+    cdef double radius = 3956 # miles
+    cdef double x = math.pi/180.0
+    cdef double a, b, theta, c
+
+    a = (90.0 - lat1)*x
+    b = (90.0 - lat2)*x
+    theta = (lon2 - lon1)*x
+    c = math.acos(math.cos(a)*math.cos(b) + math.sin(a)*math.sin(b)*math.cos(theta))
+
+    return radius*c

docs/examples/not_in_docs/great_circle/p1.py

+import math
+
+def great_circle(lon1, lat1, lon2, lat2):
+    radius = 3956 # miles
+    x = math.pi/180.0
+
+    a = (90.0 - lat1)*x
+    b = (90.0 - lat2)*x
+    theta = (lon2 - lon1)*x
+    c = math.acos(math.cos(a)*math.cos(b) + math.sin(a)*math.sin(b)*math.cos(theta))
+
+    return radius*c