fix 'jobserver unavailable: using -j1' warning for $(SUBMAKE)

- Problem is that make doesn't recognize $(SUBMAKE) as
  make, so it won't pass MAKEFLAGS and doesn't use it's
  jobserver.

- Fixed by explicitly using $(MAKE) ...

For reference:
http://www.gnu.org/software/make/manual/html_node/Error-Messages.html
http://www.gnu.org/software/make/manual/html_node/MAKE-Variable.html#MAKE-Variable
Merge pull request #1912 from MartinNowak/makeJobServer

fix 'jobserver unavailable: using -j1' warning for $(SUBMAKE)
fix Issue 12309 - The template fullyQualifiedName returns wrong result
enable Ddoc for byGrapheme
Merge pull request #1985 from WalterBright/bygrapheme

enable Ddoc for byGrapheme
Change documentation to mention aliasing self away in unaryFun/binaryFun
Fix Issue 12315 - `array` at compile-time with all types

Problem was that `emplaceRef` calls `memcpy` for some types, which is unsafe and unavailable at compile time.

https://d.puremagic.com/issues/show_bug.cgi?id=12315
Issue 3882: Explicitly capture return values for strictly pure functions returning non-void
Merge pull request #1986 from Poita/bug12315

Fix Issue 12315 - `array` at compile-time with all types
Merge pull request #1975 from nordlow/warn-unused-returns

Issue 3882: Add warning for unused returns of strictly pure function calls
Merge pull request #1983 from Philpax/patch-1

Change documentation to mention aliasing self away in unaryFun/binaryFun
Merge pull request #1982 from 9rnsr/fix12309

Issue 12309 - The template fullyQualifiedName returns wrong result