Ensure adequate code coverage from std.random.RandomSample unittests.

The old unittests were missing coverage of large sections of
RandomSample.skip() because the ratios of sample size to source size
were such that Algorithm A was always being chosen over Algorithm D.

The new unittests fix this and also extend coverage to a number of
other areas previously not addressed.  There are also currently-failing
tests commented out with version(none) that can be used to verify
future bugfixes and improvements.

A few lines in skip() remain uncovered simply because they depend on
runtime conditions that are extremely rare.
Complete code coverage for Xorshift unittests.

Unittests for Xorshift were previously failing to cover the
constructor, and the .seed(), .save and .opEquals() methods.
Complete non-static code coverage for LinearCongruentialEngine unittests.

Unittests for LinearCongruentialEngine were previously missing the
constructor and the .save and .opEquals() methods.

Code coverage analysis still fails to pick up on the static methods
and the contents of a static if scope in lines 374-382 of .popFront().
Unittest for MersenneTwisterEngine .save.
Remove superflous assert(false) and return statements.
Many asserts in std.random can be made static.
Unittesting uriLength and emailLength

Previously untested. Pushes code coverage from 57% to 79%.
Remove debug printfs from std/uri
Style fixes in std/uri

- indentation within blocks
- braces on their own lines
Issue 10408 - Fix compile error with multiple-function reduce on a const range.
Fix Issue 9607 - std.random.randomShuffle() and partialShuffle()
don't work with Xorshift.

This is an instance of Issue 2803, a clash between a template
parameter and a default argument.  I've used the workaround
proposed in that issue thread:
http://d.puremagic.com/issues/show_bug.cgi?id=2803#c1

Tests have been included to ensure that these functions work
with all possible RNG types.
Fix save in filter.

filterBidir was actually correct.
Merge pull request #1363 from monarchdodra/filterSave

Fix save in filter.
Merge pull request #1361 from irritate/issue_10408

Issue 10408 - Fix compile error with multiple-function reduce on a const...
Restrict PseudoRngTypes access to package level.
Issue 5692 - Fix printing of complex numbers with a negative imaginary part.
Removes redundant plus sign before the negative sign.
http://d.puremagic.com/issues/show_bug.cgi?id=5692
Merge pull request #1366 from irritate/issue_5692

Issue 5692 - Fix printing of complex numbers with a negative imaginary p...
Deglobalize default threshold value, and fix initialization of threshold variable.
Fixes Issue 10468 - Remove ref from parameter type in lockstep, which caused a regression.
Fixes Issue 10469 - Remove WinAPI prototypes and enums from std.process.