Introduce a new way of building: before any file is compiled
all source files are combined into a single C file and all
header files into a single H file (per subdir).
This new approach makes it possible to quickly integrate JerryScript
into other projects:
```
$ gcc -o demo demo.c jerryscript.c jerryscript-port-default.c -lm
```
To use the source generator run:
```
$ cmake -Bbuild_dir -H. -DENABLE_ALL_IN_ONE_SOURCE=ON
$ make -C build_dir generate-single-source
```
This will create the following files in the `build_dir`:
* jerryscript.c
* jerryscript.h
* jerryscript-config.h
* jerryscript-port-default.c
* jerryscript-port-default.h
JerryScript-DCO-1.0-Signed-off-by: Peter Gal pgal.u-szeged@partner.samsung.com
