Update concepts.dd

The old version of isprime would return false for 2 and return true for any n with no factor less than sqrt(n).

These alterations fix that.
Update concepts.dd

in function isPrime: reversed the change to the condition in the loop. Changed name to isPrime in keeping with style guide.
Update concepts.dd

in isPrime: fixed braces style and corrected inequality.
Merge pull request #244 from John-Colvin/patch-1

fix the algorithm in the isprime example
Added missing dup property

For some reason dup wasn't documented for AAs.
Merge pull request #249 from John-Colvin/patch-2

Added missing dup property
Clarify wording of D variadic functions

It said that _argptr "enables the creation of typesafe variadic
functions". This is misleading, since the  next section is titled
"Typesafe variadic functions" but means something different!
Merge pull request #251 from donc/typesafevariadic

Don't describe D variadic functions as "typesafe variadic"
rebase
Updated FAQ links to the new wiki
Merge pull request #253 from lmbarros/patch-1

Updated FAQ links to the new wiki
Remove all $(V1 ...) macro calls
Remove $(V2 ...) macro (leaving its contents)
Merge pull request #255 from leandro-lucarella-sociomantic/remove-v1-v2-macros

Remove $(V1/2 ...) macros
Replace $(AMP) with "and" in title

Avoids anchor breakage.
Avoid $(AMP) in title

See previous commit.
rebased
Merge remote-tracking branch 'myfork/master'
fix more rebase errors
proverbial last bug