Get rid of spaces between arguments on test help screen.

It makes it easier to read, since the number of options is getting
quite big.

(cherry picked from commit 480f68d2f4772e7a802851f772da66b6ca368831)
Casting necessary for the case size_t is smaller than int.

(cherry picked from commit 9effa9c17c4795e4e593b091913f993efe1f2119)
Casting is not needed, but is good practice

Always cast negative values in unsigned types since in some cases bugs
might be hidden. See:

https://www.securecoding.cert.org/confluence/display/seccode/INT18-C.+Evaluate+integer+expressions+in+a+larger+size+before+comparing+or+assigning+to+that+size#INT18-C.Evaluateintegerexpressionsinalargersizebeforecomparingorassigningtothatsize-NoncompliantCodeExample%28size_t%29
(cherry picked from commit 6c03d55a60af061e3238608e0f902b79c9c9b6b0)
Turn on reverse DNS lookups when there are admit_hostname rules.

(cherry picked from commit 16035ec51913f082dd997f9c81055f370173d72c)
Rename variable masking identically named variable of different type.

(cherry picked from commit bf9b17e9afe9a18d82deb72cf6d157f2d8af8b7e)
Clarification comment.

(cherry picked from commit 24080a967ffcdd0d860762d949f2f35ccd5a5f89)
Acceptance tests for admit_hostnames and deny_hostnames.

(cherry picked from commit 10765ffa01ca06c1211f050913650dbd4deb4f4f)