Add error handling and optimize FileIO::doBuffer() in the Bridge library

Update FileIO::doBuffer() to check for TRANSFER_TIMEOUT and set buffered to 0, and optimize by incrementing readPos instead of moving all of the data one byte to the left in the buffer to skip the error code byte.
Merge tag '1.0.5-r2' into HEAD
New common AVR toolchain
Added missing DLLs
Fixed MacOSX AVR toolchain .zip checksum
Updated avr toolchain for macosx: should be compatible with macosx 10.6+ (was 10.7+)
Make some operators in IPAddress const

These functions do not modify the IPAddress object, but were not marked
as const. This meant that you could not do:

void set_ip(const IPAddress& ip) {
	uint32_t copy = ip;
}

Since calling operator uint32_t() on ip would discard the constness of
the reference.
Merge remote-tracking branch 'matthijs/ide-1.5.x-ipaddress-const' into ide-1.5.x
Remove duplicate code from HardwareSerial::begin() methods.

There are two begin methods, one which accepts just a baud rate and
uses the default bit settings and one which accepts both a baudrate and
a bit config. Previously, both of these contained a complete
implementation, but now the former just calls the latter, explicitely
passing the default 8N1 configuration.

Technically, this causes a small change: Before the UCSRC register was
untouched when calling begin(baud), now it is explicitely initialized
with 8N1. However, since this is the default configuration for at least
the Uno and the Mega (didn't check any others), probably for all avrs,
this shouldn't effectively change anything. Given that the Arduino
documentation also documents this as the default when none is passed,
explicitly setting it is probably a good idea in any case.
Slightly reduce code utilization by inlining HardwareSerail begin(baud) and operator bool()
Remove unused variable
Simplify HardwareSerial::begin()

This simplifies the baud rate calculation, removing the need for a goto
and shortening the code a bit. Other than that, this code should not use
any different settings than before.

Code was suggested by Rob Tillaart on github.

Closes: #1262
Define a _NOP() macro

Recent avr-libc releases define one, but this allows using it also on
older avr-libc releases.
Use constants for register bit positions in HardwareSerial

Previously, the constants to use for the bit positions of the various
UARTs were passed to the HardwareSerial constructor. However, this
meant that whenever these values were used, the had to be indirectly
loaded, resulting in extra code overhead. Additionally, since there is
no instruction to shift a value by a variable amount, the 1 << x
expressions (inside _BV and sbi() / cbi()) would be compiled as a loop
instead of being evaluated at compiletime.

Now, the HardwareSerial class always uses the constants for the bit
positions of UART 0 (and some code is present to make sure these
constants exist, even for targets that only have a single unnumbered
UART or start at UART1).

This was already done for the TXC0 constant, for some reason. For the
actual register addresses, this approach does not work, since these are
of course different between the different UARTs on a single chip.

Of course, always using the UART 0 constants is only correct when the
constants are actually identical for the different UARTs. It has been
verified that this is currently the case for all targets supported by
avr-gcc 4.7.2, and the code contains compile-time checks to verify this
for the current target, in case a new target is added for which this
does not hold. This verification was done using:

for i in TXC RXEN TXEN RXCIE UDRIE U2X UPE; do echo $i; grep --no-filename -r "#define $i[0-9]\? " /usr/lib/avr/include/avr/io* | sed "s/#define $i[0-9]\?\s*\(\S\)\+\s*\(\/\*.*\*\/\)\?$/\1/" | sort | uniq ; done

This command shows that the above constants are identical for all uarts
on all platforms, except for TXC, which is sometimes 6 and sometimes 0.
Further investigation shows that it is always 6, except in io90scr100.h,
but that file defines TXC0 with value 6 for the UART and uses TXC with
value 0 for some USB-related register.

This commit reduces program size on the uno by around 120 bytes.
Move interrupt handlers into HardwareSerial class

The actual interrupt vectors are of course defined as before, but they
let new methods in the HardwareSerial class do the actual work. This
greatly reduces code duplication and prepares for one of my next commits
which requires the tx interrupt handler to be called from another
context as well.

The actual content of the interrupts handlers was pretty much identical,
so that remains unchanged (except that store_char was now only needed
once, so it was inlined).

Now all access to the buffers are inside the HardwareSerial class, the
buffer variables can be made private.

One would expect a program size reduction from this change (at least
with multiple UARTs), but due to the fact that the interrupt handlers
now only have indirect access to a few registers (which previously were
just hardcoded in the handlers) and because there is some extra function
call overhead, the code size on the uno actually increases by around
70 bytes. On the mega, which has four UARTs, the code size decreases by
around 70 bytes.
Merge branch 'ide-1.5.x' into ide-1.5.x-avr-toolchain
Wire library, move hard references IRQn to defines in variant.h
Toolchains updated, sha1sum updates follow
better Client.stop() handling in WebClientRepeating and WifiWebClientRepeating examples
Compile with -x assembler-with-cpp instead of -assembler-with-cpp.

- Newer avr-gcc doesn't use -assembler-with-cpp, but
  uses -x assembler-with-cpp. This works with older compilers as well.