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).
Merge branch 'master' of github.com:chapel-lang/chapel into add-warnings-opt
Update documentation for new WARNINGS variable in makefiles.
Fix comment about nighly and CHPL_DEVELOPER.
Merge branch 'master' of github.com:chapel-lang/chapel into add-warnings-opt
Merge pull request #594 from thomasvandoren/add-warnings-opt

Enable C compiler warnings without setting CHPL_DEVELOPER.

Add new WARNINGS var in Makefiles. Set to 1 when CHPL_DEVELOPER is
defined. 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).