sort: Fix two bugs with determining the end of field

* src/sort.c: When no specific number of chars to skip
is specified for the end field, always skip the whole field.
Also never include leading spaces from next field.
* tests/misc/sort: Add 2 new tests for these cases.
* NEWS: Mention this bug fix.
* THANKS: Add bug reporter.
Reported by Davide Canova.

tests/misc/sort

@@ -110,6 +110,8 @@ my @Tests =
 ["07b", '-k 2,3', {IN=>"a a b\nz a a\n"}, {OUT=>"z a a\na a b\n"}],
 ["07c", '-k 2,3', {IN=>"y k b\nz k a\n"}, {OUT=>"z k a\ny k b\n"}],
 ["07d", '+1 -3', {IN=>"y k b\nz k a\n"}, {OUT=>"z k a\ny k b\n"}],
+# ensure a character position of 0 includes whole field
+["07e", '-k 2,3.0', {IN=>"a a b\nz a a\n"}, {OUT=>"z a a\na a b\n"}],
 #
 # report an error for `.' without following char spec
 ["08a", '-k 2.,3', {EXIT=>2},
@@ -210,6 +212,10 @@ my @Tests =
 # key start and key end.
 ["18e", '-nb -k1.1,1.2', {IN=>" 901\n100\n"}, {OUT=>"100\n 901\n"}],
 
+# When ignoring leading blanks for end position, ensure blanks from
+# next field are not included in the sort. I.E. order should not change here.
+["18f", '-k1,1b', {IN=>"a  y\na z\n"}, {OUT=>"a  y\na z\n"}],
+
 # This looks odd, but works properly -- 2nd keyspec is never
 # used because all lines are different.
 ["19a", '+0 +1nr', {IN=>"b 2\nb 1\nb 3\n"}, {OUT=>"b 1\nb 2\nb 3\n"}],