diffs: add test coverage of inline diff with other markup

Add trailing whitespaces ... but also whitespace before changes (which might
seem trailing but isn't).

kallithea/tests/fixtures/markuptest.diff

@@ -1,7 +1,7 b''
 diff --git a/f b/f
 --- a/f	
 +++ b/f	
-@@ -51,6 +51,13 @@
+@@ -51,8 +51,15 @@
  	begin();
  	
 +	int foo;
@@ -17,3 +17,6 b' diff --git a/f b/f'
  
 -	#define MIN_STEPS (48)
 +	#define MIN_STEPS (42)
+ 
+-	#define MORE_STEPS	+(48)	
++	#define LESS_STEPS	(42) 

kallithea/tests/models/test_diff_parsers.py

@@ -351,7 +351,7 b' class TestDiffLib(base.TestController):'
             l.append('%(action)-7s %(new_lineno)3s %(old_lineno)3s %(line)r\n' % d)
         s = ''.join(l)
         assert s == r'''
-context         '@@ -51,6 +51,13 @@'
+context         '@@ -51,8 +51,15 @@'
 unmod    51  51 '<u>\t</u>begin();'
 unmod    52  52 '<u>\t</u><i></i>'
 add      53     '<u>\t</u>int foo;<u class="cr"></u>'
@@ -367,4 +367,7 b" add 61 '<u>\\t</u>#define MAX_ST"
 unmod    62  55 ''
 del          56 '<u>\t</u>#define MIN_STEPS (<del>48</del>)'
 add      63     '<u>\t</u>#define MIN_STEPS (<ins>42</ins>)'
+unmod    64  57 ''
+del          58 '<u>\t</u>#define <del>MORE_STEPS</del><u>\t</u><del>+</del>(<del>48</del>)<del><u>\t</u></del><del><i></i></del>'
+add      65     '<u>\t</u>#define <ins>LESS_STEPS</ins><u>\t</u>(<ins>42</ins>)<ins> <i></i></ins>'
 '''