if a needed CONNECT tunnel fails

connections are now retried after timeout and failing connections will
be marked as skipped instead of failing. This should reduce false alarms
on travis

add test case new Input check
add global variables to execute

this should help with applying pull requests that do come not from the
translation interface as it makes sure the files will be at least
syntactically correct.

Since a8dba452 the search index didn't
properly index numeric words anymore, instead they were added as new
words to the word list each time they were indexed, leading to an
ever-increasing index size.

This fixes sending empty and duplicated To/Cc/Bcc, Subject and From
headers in the additional headers. The To-header in the additional
headers prevented mail sending on some systems.

Prevent table entry syntax swallowing multiple preceeding blank lines
(a) this shouldn't be necessary, blank lines are handled by paragraph
    processing
(b) avoids issues with greedy table syntax competing with plugins

ensure css loadfile test doesn't try to create a directory (and fail) if the directory already exists

This test is horrible, but I believe necessary to ensure that the
@import of less files actually works.

It is horrible as its not a unit test and its not a true functional
test.  It probably implies the code in css_out() should be refactored
to make it easier to test intermediate results.

- use TMP_DIR constant rather than /tmp
- swap order of parameters in csstest() to match reported 'expected' & 'actual'
- add tests for use of 'url()' in @import
- add tests for @import of '.less' files (these test will fail per FS#2875)