Disable --gdb execopt on darwin.

Darwin now supports only lldb, so we would have to make the behavior
of the --gdb option platform-dependent.  (That is, start lldb if
running on darwin.)

Separate tests would probably be needed for this option, so just
not testing it on darwin for now.
Modify declint2.prediff to remove leading ./ from gdb output of PGI debug data.
Fix a race in studies/jacobi/waynew/example2.chpl

This test had been very rarely generating incorrect output due to failing to
detect that sufficient change had occurred between late passes.  This happened
because the variable used to determine if sufficient change had occurred was
being updated by all running tasks without locking so there was a race.  Since
we don't support atomic |= for booleans, I replaced the boolean with an atomic
integer, and the |= call with atomically adding the old boolean check (so if
the result of comparing the new and old values was above the tolerance for a
change, then an integer representation of true would be added).  After 150 runs,
it appears that this has solved the problem.
Brad pointed out that this should skip with valgrind EXE, not COMP
Merge pull request #719 from lydia-duncan/fixJacobiRace

Fix a race in studies/jacobi/waynew/example2.chpl [suggested by Brad]

This test had been very rarely generating incorrect output due to failing to
detect that sufficient change had occurred between late passes. This happened
because the variable used to determine if sufficient change had occurred was
being updated by all running tasks without locking, so there was a race. Since
we don't support atomic |= for booleans, I replaced the boolean with an atomic
integer, and the |= call with atomically adding the old boolean check (so if
the result of comparing the new and old values was above the tolerance for a
change, then an integer representation of true would be added). After 150 runs,
it appears that this has solved the problem (100 runs was sufficient to see 6
failures in this manner with fifo before this change).
Merge pull request #720 from lydia-duncan/tooManyThreadsForValgrind

Brad pointed out that this should skip with valgrind EXE, not COMP
Quiet align.chpl errors with Intel and PGI compilers.

The odd behavior on Intel and PGI compilers was due to how a 32-bit temporary was being
inlined:
 - On GCC, the declared size of the temporary (int32_t) was being obeyed, either by being
    written back to a 32-bit memory location, or by being sign-extended inline.
 - On Intel and PGI, the 32-bit result was stored in a 64-bit register and not 32-bit
    sign-extended.

The intent of the test was to demonstrate correct behavior with the first 64-bit integer
not representable as a 32-bit integer.  To avoid compiler dependencies, this constant is
now hard-coded.

The compiler-dependent behavior is captured in a new future with a suggestion for
specifying the behavior that is expected.
Add missing EOL on constOverflow.skipif
Reserving various symbols that appear in darwin
Quiet execflags/bradc/gdbddash/declint2 output on PrgEnv-pgi

The existing prediff script looks for "gdbShouldBreakHere" but in the fast tests, GDB
doesn't print it out at all.

Under PGI, the breakpoint location is printed out with a leading dot-slash.

I solved both problems by modifying the prediff to look for the runtime output
  declint2.chpl:7: error: halt reached - array index out of bounds: (0)
instead.

Since the point of the test is to show that we can run under GDB, if we get as far as
generating error output, we have run the program.  Done.
Merge pull request #722 from benharsh/reserve-darwin

Reserving various symbols that appear on darwin

This patch should fix the darwin compilation errors for compSampler*. 'fls' is the name of a function in darwin, and should become a reserved word in Chapel to avoid compilation errors.

These changes should also fix parallel/sync/diten/userLevelEndCount . The 'wait' function can conflict with darwin functions (wait2/3/4) during C compilation.
Modifications in response to Brad's review.

Use max(int(32)):int(64) + 1 in place of a literal constant.

Removed the "Chapel should ..." phrase.

Added detail to the future, to suggest that runtime overflow checking could be on by
default in debug mode and off by default when optimizations are enabled.
Merge pull request #723 from hildeth/quietGDBdarwin

Quiet gdb execopts test on darwin and PGI platforms.
Merge pull request #721 from hildeth/quietAlignErrors

Quiet align.chpl errors on Intel and PGI.

Changed align.chpl to better demonstrate the original intent.
Added a new future to demonstrate the compiler-dependent behavior.
Suppress constOverflow test when CHPL_TARGET_COMPILER==clang.
Disable static_dynamic for cygwin

This test depends on the file command displaying the link status of the
executable.  However, cygwin's files are in PE format - the file command does
not display many details about this format and I wasn't seeing an option that
would enable it to display correctly.  So, skip it here.
Fix prediff in prgenv-* cases for static_dynamic

The cray programming environments link statically by default, as opposed to
our usual environments which default to dynamic.  The prediff for this test
attempted to take that into account, but was checking against the wrong
environment variable to do so.  Fixing that.
The static flag is not supported on darwin, so skip this test there.
Add declint2.skipif to skip when --fast is tossed.

This test (declint2) is intende to show that GDB will stop when a deliberate
out-of-bounds array access is attempted.  But bounds checking is turned off when
--fast is tossed, so this test does not pertain.
r