Problem: Various inconsistencies in test files.
Solution: Add modelines where they were missing. Use Check commands instead
of silently skipping over tests. Adjust indents and comments.
(Ken Takata, closes#6695)
Problem: assert_fails() checks the last error message.
Solution: Check the first error, it is more relevant. Fix all the tests
that rely on the old behavior.
Problem: Compiling weird regexp pattern is very slow.
Solution: When reallocating post list increase size by 50%. (Kuang-che Wu,
closes#4012) Make assert_inrange() accept float values.
Problem: Internal error when using pattern with NL in the range.
Solution: Use an actual newline for the range. (closes#3989) Also fix
error message. (Dominique Pelle)
Problem: Old regexp engine may use invalid buffer for 'iskeyword' or
uninitialized buffer pointer. (Kuang-che Wu)
Solution: Set rex.reg_buf when compiling the pattern. (closes#3972)
Problem: The new regexp engine does not give an error for using a back
reference where it is not allowed. (Dominique Pelle)
Solution: Check the back reference like the old engine. (closes#1774)
Problem: Regexp fails to match when using "\>\)\?". (Ramel)
Solution: When a state is already in the list, but addstate_here() is used
and the existing state comes later, add the new state anyway.
Problem: The example that explains nested backreferences does not work
properly with the new regexp engine. (Harm te Hennepe)
Solution: Also save the end position when adding a state. (closes#990)
