add Buffer::Iterator::{prev,next}()

src/core/Buffer-Iterator.cc

@@ -201,3 +201,17 @@ void Buffer::Iterator::warp_to_offset(size_t offset)
         }
     }
 }
+
+Buffer::Iterator Buffer::Iterator::prev()
+{
+    Iterator i = *this;
+    i.go_back();
+    return i;
+}
+
+Buffer::Iterator Buffer::Iterator::next()
+{
+    Iterator i = *this;
+    i.go_forward();
+    return i;
+}

src/core/Buffer.h

@@ -41,6 +41,8 @@ public:
         bool go_right_in_line(bool allow_eol);
         bool go_previous_line();
         bool go_next_line();
+        Iterator prev();
+        Iterator next();
         void warp(ssize_t offset_offset, ssize_t line_offset)
         {
             m_offset += offset_offset;