Parser: Test for exact missing ':' location column

This ensures compiler points to the right place when claiming that ':' is
missing.

tests/parser/tinvcolonlocation2.nim

@@ -0,0 +1,15 @@
+discard """
+  file: "tinvcolonlocation2.nim"
+  line: 11
+  column: 1
+  errormsg: "':' expected"
+"""
+try:
+  echo "try"
+except #<- missing ':'
+  echo "except"
+finally:
+#<-- error will be here above, at the beginning of finally,
+#    since compiler tries to consome echo and part of except
+#    expression
+  echo "finally"