Reported by: Ethan Burns, Rich Prohaska, Tudor Bosman

Fix prof_lookup() to artificially raise curobjs for all paths through
the code that creates a new entry in the per thread bt2cnt hash table.
This fixes a race condition that could corrupt memory if prof_accum were
false, and a non-default lg_prof_tcmax were used and/or threads were
destroyed.

Fix realloc() such that it only records the object passed in as freed if
no OOM error occurs.

Add a missing prof_malloc() call in allocm().  Before this fix, negative
object/byte counts could be observed in heap profiles for applications
that use allocm().

Rewrite prof_alloc_prep() as a cpp macro, PROF_ALLOC_PREP(), in order to
remove any doubt as to whether an additional stack frame is created.
Prior to this change, it was assumed that inlining would reduce the
total number of frames in the backtrace, but in practice behavior wasn't
completely predictable.

Create imemalign() and call it from posix_memalign(), memalign(), and
valloc(), so that all entry points require the same number of stack
frames to be ignored during backtracing.

Fix the manual page to document the swap.fds mallctl as read-write,
rather than read-only.

Conditionalize an isalloc() call in rallocm() that be unnecessary.

Properly handle boundary conditions for sampled region promotion in
rallocm().  Prior to this fix, some combinations of 'size' and 'extra'
values could cause erroneous behavior.  Additionally, size class
recording for promoted regions was incorrect.

Clean up some prof-related comments to more accurately reflect how the
code works.

Simplify OOM handling code in a couple of prof-related error paths.

Use the argument to prof_tdata_cleanup(), rather than calling
PROF_TCACHE_GET().  This fixes a bug in the NO_TLS case.

Add the --with-private-namespace option to make it possible to work
around library-private symbols being exposed in static libraries.

Fix assertions in arena_purge() to accurately reflect the constraints in
arena_maybe_purge().  There were two bugs here, one of which merely
weakened the assertion, and the other of which referred to an
uninitialized variable (typo; used npurgatory instead of
arena->npurgatory).

Add the LLU suffix for all 0x... 64-bit constants.

Reported by Jakob Blomer.

Update .gitignore and configure.ac to deal with the recent directory
restructuring.

Add a missing #ifdef to conditionally exclude code that is relevant only
to the tcache feature.

Add inline assembly implementations of atomic_{add,sub}_uint{32,64}()
for x86/x64, in order to support compilers that are missing the relevant
gcc intrinsics.

This reverts commit adc675c8.

The original commit added support for a non-standard libunwind API, so
it was not of general utility.

arena_purge() may be called even when there are no dirty pages, so
loosen an assertion accordingly.

Use libunwind's unw_tdep_trace() if it is available.

sa2u() returns 0 on overflow, but the profiling code was blindly calling
sa2u() and allowing the error to silently propagate, ultimately ending
in a later assertion failure.  Refactor all ipalloc() callers to call
sa2u(), check for overflow before calling ipalloc(), and pass usize
rather than size.  This allows ipalloc() to avoid calling sa2u() in the
common case.

Add code to set *rsize even when profiling is enabled.

Initialize arenas_tsd earlier, so that the non-TLS case works when
profiling is enabled.

Fix a regression due to:
    Remove an arena_bin_run_size_calc() constraint.
    2a6f2af6
The removed constraint required that small run headers fit in one page,
which indirectly limited runs such that they would not cause overflow in
arena_run_regind().  Add an explicit constraint to
arena_bin_run_size_calc() based on the largest number of regions that
arena_run_regind() can handle (2^11 as currently configured).

Dynamically adjust tcache fill count (number of objects allocated per
tcache refill) such that if GC has to flush inactive objects, the fill
count gradually decreases.  Conversely, if refills occur while the fill
count is depressed, the fill count gradually increases back to its
maximum value.

pthread_mutex_lock() can call malloc() on OS X (!!!), which causes
deadlock.  Work around this by using spinlocks that are built of more
primitive stuff.

Import updated pprof from google-perftools 1.7.

Add atomic.[ch], which should have been part of the previous commit.

Add the "stats.cactive" mallctl, which can be used to efficiently and
repeatedly query approximately how much active memory the application is
utilizing.

Rather than blindly assigning threads to arenas in round-robin fashion,
choose the lowest-numbered arena that currently has the smallest number
of threads assigned to it.

Add the "stats.arenas.<i>.nthreads" mallctl.