Buffer begin and end are not end-of-words

Buffer begin never has a word character before, and end is always
preceeded by an end-of-line.

Fixes #2420

src/buffer_utils.hh

@@ -63,7 +63,7 @@ inline bool is_bow(const Buffer& buffer, BufferCoord coord)
 inline bool is_eow(const Buffer& buffer, BufferCoord coord)
 {
     if (buffer.is_end(coord) or coord == BufferCoord{0,0})
-        return true;
+        return false;
 
     auto it = utf8::iterator<BufferIterator>(buffer.iterator_at(coord), buffer);
     return is_word(*(it-1)) and not is_word(*it);

test/regression/2420-discrepancy-in-star-behaviour/cmd

@@ -0,0 +1 @@
+x*n

test/regression/2420-discrepancy-in-star-behaviour/in

@@ -0,0 +1,3 @@
+a
+
+%(a)

test/regression/2420-discrepancy-in-star-behaviour/state

@@ -0,0 +1 @@
+1.1,1.2