Add new WARNINGS var in Makefiles. Set to 1 when CHPL_DEVELOPER is defined.

WARNINGS will be used to enable and disable compiler warnings in
make/compiler/Makefile.* files. At present, those Makefiles enable and disable
warnings based on CHPL_DEVELOPER. There are situations where CHPL_DEVELOPER is
not set, but compiler warnings are wanted.
Use WARNINGS to enable warning flags in compiler specific makefiles.

Previously whether or not CHPL_DEVELOPER was defined determined if the warning
flags were added for C compiler. Instead, use the WARNINGS variable. This
allows a developers to build with compiler warnings enabled (e.g. when building
the runtime/) without the rest of the CHPL_DEVELOPER settings. Conversely, if
CHPL_DEVELOPER is set, a developer can disable C compiler warning flags by
setting WARNINGS=0 when calling make. The latter is not especially useful (or
recommended).
Copy .bash versions of setchplenv to .zsh version.
bash -> zsh
Merge branch 'master' of github.com:chapel-lang/chapel into add-warnings-opt
Update documentation for new WARNINGS variable in makefiles.
Cleanup output of .sh versions of setchplenv.

Use printf to print strings that should not have a new line char. I copied the
.bash versions and substitued `printf` for `echo -n`.
Add %s format argument to printfs
Revert "Add %s format argument to printfs"

This reverts commit 0b7d971c49504e3b5ba024c6faa1079ecb4d26c4.
Revert "Cleanup output of .sh versions of setchplenv."

This reverts commit ba26a7031d1886155ebcdd8fd8e3a4de09bece37.
Revert "bash -> zsh"

This reverts commit 8abe3ce896c07d583927315bd8c9f1e7220e4103.
Revert "Copy .bash versions of setchplenv to .zsh version."

This reverts commit a0f8481be45796171b91f7b9425edefaf97a366a.
Add zsh to the list of shells that are bash-compatible.
Merge branch 'master' of github.com:chapel-lang/chapel into zsh-setchplenv
Fix comment about nighly and CHPL_DEVELOPER.
Merge branch 'master' of github.com:chapel-lang/chapel into add-warnings-opt
Add new future on the precedence of _defaultOf relative to default construction,.
Revised source after testing with default constructor def missing.
Merge pull request #623 from hildeth/master

Add a future to describe the desired precedence of _defaultOf() over default constructor calls.
Fixing quickstart shells w.r.t. quickstart on Crays problem TMac hit today

Today, TMac started up a Cray Chapel environment building from source
in which CHPL_COMM would default to gasnet/aries or gasnet/gemini due
to being on a Cray, but the CHPL_MEM layer would be set to cstdlib
because of a seemingly innocuous change made to
util/quickstart/setchplenv.* when we made tcmalloc the default.
Because these GASNet conduits require tcmalloc or dlmalloc or the like
to register memory, an (vague) error is generated.

Here I'm addressing this by:

(a) making the quickstart files set CHPL_COMM to 'none' which arguably
    is what we might want people to start with, even on a Cray if
    they're building from source (and is already the default
    everywhere else);

(b) making the quickstart files not set CHPL_MEM.  This is something
    we will probably want to undo if/when we make tcmalloc the default
    at some point in the future.

Either one of these changes should be sufficient by itself.  Both
seemed like a better reflection of what we would want the quickstart
to do when building from source today.

Note that these changes won't affect Cray module users because they
get a different README and tend not to use the setchplenv.* scripts.