simplify threadloop begin/end generation code
add test for continue in threadloop
allow use of the C continue statement at the top level of a threadloop
Fix pdl('nan') giving 0 problem

This uses get_datatype() to determine the correct datatype value
to use for the NaN piddle value.  NOTE: we need to review all the
pdl source tree for hardwired usages of datatype and fix.
Fix some POD errors

Helpfully, one can grep -R 'POD ERROR' in the HtmlDocs directory
and find these errors.  Most just needed an encoding specified
for documents with non-ASCII characters.
add vsearch_insert_leftmost, vsearch_insert_rightmost, vsearch_match, vsearch_bin_inclusive, vsearch_bin_exclusive and associated tests
code/doc generation of vsearch_* routines now table driven
don't use experimental lexical $_
test vsearch api to ensure backwards compatibility
vsearch() is now a front end to all vsearch_* routines

* old vsearch is now vsearch_sample
* clean up docs/code so signatures match documented arguments
add a test to see if at() and sclr() both return BAD values

The current issue is that `at` will return the Perl string BAD, but
`sclr` does not. This causes issues with other functions that use `sclr`
such as `minmax`.
check that stringify is overloaded

This currently fails as mentioned in <https://sourceforge.net/p/pdl/bugs/356/>.
The reason is that the overload method is `PDL::Core::string` which is
aliased to `PDL::string`. The issue is that the alias does not exist
when the overload is applied.
testing `min` and `max` behaviour with BAD values

Problems with this behaviour were brought up at
<http://mailman.jach.hawaii.edu/pipermail/pdl-porters/2014-November/006437.html>.
put the aliases in a BEGIN block so that are defined early

This fixes an issue that came up with `overload::Method()` not knowing
where `PDL::Core::string` was defined as described here
<https://sourceforge.net/p/pdl/bugs/356/>.
Merge commit '6c1737f799a18de9715d14c42f2b8d82a4154bf4'
Merge commit 'df8b4287b9f53cc71792cde3d7b5f70abeb3c704'
Add test labels to new at() and sclr() bad checks
Make new at/sclr bad test a TODO
Merge commit 'cefc1b7ebf909039a98ac684c27763193ead0e21'
Make tests TODO and add comment re perl scalar vs pdl values for BAD