Move long running test case earlier to speed up parallel testing.

This is purely an optimization. Since the test case is long running,
it should occupy a job slot early in the process, so it can chew on it
for a while, while the rest of the tests are running.

Also fix a typo in the path that has been bugging me for ages.
Make sure all relevant variables are inherited by sub invokations.

This fixes parallel test runs in sub projects.
Make sure serial tests are run, even if parallel ones fail.

This moves the serial tests out of the makefile, since make would
refuse to run them if any parallel tests had failed.
Catch errors resulting from miscalculating the number of test results.

This will save us if we make a mistake in testall which leaves out
some test results.
Comments and clarifications on the receive loop, no change in functionality.
Clarify that empty transaction payloads are not allowed

Previously they were not explicitly disallowed, but if they were sent
we'd be in trouble since ReceiveTransaction() would return 0, meaning
connection closed.
Clarify TLSSend() and SendTransaction() semantics.
Removed 'towrite' superfluous variable.
Mostly beautification.
wrapping
Beautification again, no change in functionality.
Fix very old code, if read is partial (n_read < toget) this would write garbage.
Partial transactions received should result in error.

Keep this for some time in master, if it triggers in any platform then
TLSRecv() will have to use a loop, just like RecvSocketStream().
Clarify that TLSRecv() *will* return less than what was requested, if the TLS record that was sent was smaller.
len is better as a signed int now that all proper checks are being made - fixes -Wextra compiler warning.
Satisfy -Wextra warnings by converting 'got' to unsigned type and checking for overflow.
Merge pull request #1949 from jimis/TLSRecv_clarifications

TLSRecv clarifications
Merge pull request #1970 from kacfengine/testall_fixes

Testall fixes
Redmine 6225: Disable examples checking on non-Linux platforms.