Make exception base class visible in basic_json

Instead of overwriting src/json.hpp with an empty file

Added catch branch for out_of_range exception that can occur if input
file contains a number overflow.

We should compare the binary serializations rather than the JSON values
themselves. This fix was already done for CBOR and apparently forgotten
for MessagePack.

🎨 Namespace `uint8_t` from the C++ stdlib

add to_json method for C arrays

- Removed unused headers.
- Added override where needed.
- Added description for parse_error.113 exception.
- Fixed some conversion warnings.
- Integrated cbor_expect_string function for CBOR maps.
- Added documentation on the supported CBOR/MessagePack features.
- Added test to check all initial bytes for CBOR input.

With GCC 7, there are even more diagnostic flags.

    If the array can be converted to basic_json::string_t, the overload
in this commit is not chosen.

Replaced old std::invalid_argument exception by parse_error.111 to have
unified exceptions in case of input stream errors.

Also merged develop into this feature branch.

When <Windows.h> is included with MSVC, a macro NOMINMAX is defined
that yields compilation errors when max/min calls are encountered. This
can be fixed by un-defining NOMINMAX, or by placing parentheses around
all min/max calls. We chose the latter.

Since #329, NaN and inf numbers do not yield an exception, but are
stored internally and are dumped as “null”. This commit adjusts the
fuzz testers to deal with this special case.

Removed a check that already failed in MSVC.

- If an overflow occurs during parsing a number from a JSON text, an
exception (std::out_of_range for the moment, to be replaced by a
user-defined exception #244) is thrown so that the overflow is detected
early and roundtripping is guaranteed.
- NaN and INF floating-point values can be stored in a JSON value and
are not replaced by null. That is, the basic_json class behaves like
double in this regard (no exception occurs). However, NaN and INF are
serialized to “null”.
- Adjusted test cases appropriately.

Removed some code that is not needed any more. Thus, streamlining the
array from_json methods.

These tests currently pass without any adjustments to the source code.

To avoid the error described in #497, I added a function
msgpack_expect_string that is executed every time a string is expected
during the parsing of a map. In case the current byte does not belong
to a MsgPack string, an exception is thrown.

Added all possible exceptions to the examples of the at functions.

This test case relied on logics that have been replaced by CMake with
#461. This change enables compilation and execution of the test suite
without exceptions by adding an after_success task.

Implemented std::less<value_t> to allow using value_t as std::map key
in MSVC.

Added a test to check if the input stream is good() before executing
getline on it. Also added two test cases that set the failbit and
badbit before calling file_line_buffer.

MSVC does not define __cpp_exceptions, but seems to use _CPPUNWIND when
exception support is switched on, see
https://msdn.microsoft.com/en-us/library/b0084kay.aspx.

I used __EXCEPTIONS to detect whether exceptions are supported.
Apparently, this is a macro that is only used by libstdc++
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64276). It’s much cleaner
to use __cpp_exceptions as it is in the standard since C++98.

Note that compiling the unit-tests with “-fno-exceptions” still does
not work, because Catch uses throw internally. However, the library’s
exceptions can be switched off by defining JSON_NOEXCEPTION.