folly: get building with gcc-4.7.1

Summary:
A lot of libstdc++-4.7 headers dropped includes of unistdc.h, so
we'll probably see more of these.

Test Plan: built folly

Reviewed By: simpkins@fb.com

FB internal diff: D508871
add bm_max/min_iters and bm_regex

Summary: These were handy in the old framework and easy enough to add.

Test Plan:
ran ThreadCachedIntTest - got better (but not perfect due to
subtraction of single-threaded baseline from multi-threaded results).

Reviewed By: sherman.ye@fb.com

FB internal diff: D490324
Remove unnecessary member variable.

Test Plan: No

Reviewed By: andrei.alexandrescu@fb.com

FB internal diff: D509324
adding StringPiece constructor that takes a piece of another StringPiece

Summary:
adding what seems to be a missing constructor to StringPiece --
I need to be able to take a piece of another StringPiece. (It's possible
to do that with all sorts of strings already, except StringPiece...)

Test Plan: na -- tested as part of other (dependent) diffs

Reviewed By: delong.j@fb.com

FB internal diff: D508545
Add multi-bit operations to folly/experimental/Bits.h

Summary: Add ability to set and get N consecutive bits from the bit sequence.

Test Plan: test added

Reviewed By: lucian@fb.com

FB internal diff: D511438
Improve digits_to() performance

Summary:
This optimization eliminates about 75% of the multiplications and bounds
checking in the original code by using constant lookup tables to convert
from decical digit to (shifted) binary number, instead of arithmetic.
The total cost of the lookup tables is 2KB of static memory, but the
average throughput gain across the range from 1 to 19 characters is 27%.
The throughput distributes as follows: (in million iters/sec)
Bytes   Orig    New     Speedup
1       101.31  110.12  109%
2       97.42   110.12  113%
3       97.42   105.53  108%
4       79.13   101.31  128%
5       74.48   97.42   131%
6       74.48   93.81   126%
7       70.35   93.81   133%
8       61.77   79.14   128%
9       58.9    72.35   123%
10      58.9    74.48   126%
11      56.28   74.48   132%
12      50.22   64.93   129%
13      48.52   60.3    124%
14      47.74   61.77   129%
15      46.88   61.77   132%
16      42.54   55.06   129%
17      41.51   51.69   125%
18      40.97   52.76   129%
19      39.57   52.76   133%

Test Plan: Passes all unit tests

Reviewed By: andrei.alexandrescu@fb.com

FB internal diff: D493245
Add IOBufQueue::prepend, fix bug in IOBuf::prepend.

Summary:
IOBuf::prepend needs to increment length_.

Added IOBufQueue::prepend, which uses the headroom in the first buffer
instead of growing the queue at the head.

Test Plan: tests added

Reviewed By: simpkins@fb.com

FB internal diff: D513676
(minor changes, part of unrelated diff)

Test Plan: no

Reviewed By: philipp@fb.com

FB internal diff: D512868
folly: fix build on ubuntu and fedora platforms

Summary:
A boost regex dependency wasn't added to the Makefile.am file.  Also
the it appears that boost thread lib dependencies had a typo in the
makefile variable name.

Test Plan: ran builds on ubunutu and fedora VMs

Reviewed By: tudorb@fb.com

FB internal diff: D514039
fix memory order in AtomicHashMap<>::findInternal()

Summary:
Looks like a typo, it should obviously be std::memory_order_relaxed (all
necessary synchronization is done on numMapsAllocated_).

Test Plan: compiled it, ran tests

Reviewed By: sahrens@fb.com

FB internal diff: D515322
folly/Malloc.h: use libstdc++-safe exception wrappers

Summary:
gcc errors out when code that throws is compiled with
'-fno-exceptions'.  Since we add Malloc.h into our custom libstdc++
use the exception wrappers from functexcept.h so that they can build
with third-party projects that use '-fno-exceptions'.

Test Plan:
Built llvm in the gcc-4.7.1-glibc-2.14.1-fb platform with these
changes.

Reviewed By: tudorb@fb.com

FB internal diff: D516577
Make Bits<T> work with T = Unaligned<X> (X is unsigned integral type)

Test Plan: all folly tests

Reviewed By: andrei.alexandrescu@fb.com

FB internal diff: D517118
(minor changes, part of unrelated diff)

Test Plan: No

Reviewed By: lucian@fb.com

FB internal diff: D515713
Range<const char*> -> Range<const unsigned char*> implicit conversion

Summary: As they can both be used to represent ranges of bytes.

Test Plan: test added

Reviewed By: andrei.alexandrescu@fb.com

FB internal diff: D518666
Unbreak build.

Summary: I could have sworn I undid that un-templatification of the constructor.

Test Plan: build folly/test

Reviewed By: andrei.alexandrescu@fb.com

FB internal diff: D518981
A sample diff thats ports FormatTests to benchmarks

Summary:
Is there any better solution? Maybe a generic flag in Benchmarks to say
please don't run benchmarks?

Test Plan: (not in folly)

Reviewed By: andrei.alexandrescu@fb.com

FB internal diff: D503619
rallocm(ALLOCM_ZERO) only zeroes *new* memory

Summary:
If you allocate N bytes and then try to grow that in place using rallocm
(ALLOCM_ZERO | ALLOCM_NO_MOVE) to M > N, our code assumed that all
memory from N to M would be zeroed.  In fact, rallocm only zeroes *new*
memory, so if jemalloc actually allocated N1 > N bytes initially,
rallocm will only zero memory from N1 to M.

Fixed by using calloc.

Test Plan: thread_local_test, tested in production

Reviewed By: delong.j@fb.com

FB internal diff: D519781