* NAN is not defined on some platform
  * follow the comment on PR

 * test build on VS2012

  * NAN is not defined on some platform

Major changes:

- modify the Base64 functions to compatible with `cvWriteRawData` and so
on.
- add a Base64 flag for FileStorage and outputs raw data in Base64
automatically.
- complete all  testing and documentation.

AutoBuffer::allocate(nsz) didn't work properly when
(sz < nsz < fixed_size). In this case sz remained unchanged.

I could not find the cause of the error:

```
C:\builds_ocv\precommit_opencl\opencv\modules\ts\src\ts_perf.cpp(361):
error: The difference between expect_max and actual_max is
8445966.0000002384, which exceeds eps, where

expect_max evaluates to 0.9999997615814209,

actual_max evaluates to 8445967, and

eps evaluates to 1.0000000000000001e-005.

Argument "dst0" has unexpected maximal value
```

Hope this is a false alarm.

The three new functions:

```cpp
void cvStartWriteRawData_Base64(::CvFileStorage * fs, const char* name,
int len, const char* dt);
void cvWriteRawData_Base64(::CvFileStorage *
fs, const void* _data, int len);
void
cvEndWriteRawData_Base64(::CvFileStorage * fs);
```

Test is also updated. (And it's remarkable that there is a bug in
`cvWriteReadData`.)

```cpp
cvWriteMat_Base64(::cv::FileStorage & fs, ::cv::String const & name,
::cv::Mat const & mat)
```
becomes:
```cpp
CV_EXPORTS void cvWriteMat_Base64(::CvFileStorage* fs, const char* name,
const ::CvMat* mat);
CV_EXPORTS void
cvWriteMatND_Base64(::CvFileStorage* fs, const char* name, const
::CvMatND* mat);
```

Two other test are still needed.

1. Verify the Base64 data.
2. Read an old YML file for compatibility test.

1. Add Base64 support for reading and writing XML\YML file.

The two new functions for writing:

```cpp
void cvWriteRawData_Base64(cv::FileStorage & fs, const void* _data, int
len, const char* dt);
void cvWriteMat_Base64(cv::FileStorage & fs, cv::String const & name,
cv::Mat const & mat);
```

2. Change YML file header form `YAML:1.0` to `YAML 1.0`. (standard
format)

3. Add test for Base64 part.

[GSoC] FileStorage:
Add base64 support for reading and writting XML\YML file.
The two new functions:
```
void cvWriteRawData_Base64(cv::FileStorage & fs, const void* _data, int
len, const char* dt);
void cvWriteMat_Base64(cv::FileStorage & fs, cv::String const & name,
cv::Mat const & mat);
```

  * remove useHW option
  * update test

  * check compiler support
  * check HW support before executing
  * add test doing round trip conversion from / to FP32
  * treat array correctly if size is not multiple of 4
  * add declaration to prevent warning
  * make it possible to enable fp16 on 32bit ARM
  * let the conversion possible on non-supported HW, too.
  * add test using both HW and SW implementation

  * fix issue #6536
  * increase threshold in particular tests due to the difference of fmsub and fsub

  * fix issue 6521
  * use correct comparison

1) fix multichannel support
2) remove useless bad_value, read value from original Mat directly
3) add more tests
4) fix docs for cvCeil and checkRange