Adjust CMakeLists.txt and .def: add _d postfix onto jansson_d.lib/dll

Had to remove the "LIBRARY" line from jansson.def, which was optional,
and was overriding CMake's desire for a specific name.
Added missing rv check - caught by clang
Merge pull request #121 from jjwchoy/master

Added missing return valua check in test
Implemented a decode option to only decode numbers to reals and never integers
Added a simple test for the JSON_DECODE_NO_INT option
Merge pull request #120 from paulharris/mine_pre_2.5

Adjust CMakeLists.txt and .def: add _d postfix onto jansson_d.lib/dll
Renamed flag to JSON_DECODE_INT_AS_REAL and added documentation
Changed :versionadded for JSON_DECODE_INT_AS_REAL docs
Using jsonp_strtod instead of casting to double to catch double overflow
Merge pull request #123 from jjwchoy/decode-ignore-int

Implemented a decode option to only decode numbers to reals
Fix indentation in docs
Tweak the JSON_DECODE_INT_AS_REAL test introduced in #123

Only run the imprecision part if json_int_t is long long, otherwise
the imprecision cannot be tested against json_int_t.

Also, convert the double value to json_int_t before checking the
imprecision, because otherwise the json_int_t is converted to double
and the imprecision happens in the "wrong direction".
Prevent unused-variable warning
Merge pull request #125 from jjwchoy/master

Prevent compiler warning
Adding option for MSVC for those who are linking statically.
Update CMakeLists.txt
Merge pull request #127 from cryptobiote/master

Adding option for MSVC for those who are linking statically.
BUGFIX: Compilation error with -DNDEBUG defined.

When building a "MinSizeRel" with CMake I get a compilation error in lex_unget_unsave. This is because assertions are turned off using -DNDEBUG:

```
/usr/bin/gcc  -DHAVE_CONFIG_H -fPIC -Os -DNDEBUG -Ijansson/build/include -Ijansson/build/private_include    -Wall -Wextra -Wdeclaration-after-statement -Werror -o CMakeFiles/jansson.dir/src/load.c.o   -c jansson/src/load.c
jansson/src/load.c: In function âx_unget_unsaveâjansson/src/load.c:256:14: error: variable â set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors
```

This will then remove the insert, which makes the "d" variable unused, which is treated as an error since we have -Wall set. We can't simply get rid of the variable either and put the strbuffer_pop call in the assert call, since it's a macro and would remove the call entirely. So I simply added a check for NDEBUG to fix it.
Merge pull request #128 from JoakimSoderberg/lex_unget_unsave_fix

BUGFIX: Compilation error with -DNDEBUG defined.
Make the argument of json_deep_copy() const

Fixes #126.