Add missing include in jm_locale_test.c

[joakimono]

One some platforms (Macos), compilation of Test/jm_locale_test.c fails, since exit() is undefined.
The solution is to #include <stdlib.h>, as is done in e.g. Test/fmi_zip_zip_test.c

[modelonrobinandersson]

Hi @joakimono, what is the error you see on MacOS?

[joakimono]

On MacOS the following error occurs:
../build/src/Test/jm_locale_test.c:30:5: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration] exit(CTEST_RETURN_FAIL); ../build/src/Test/jm_locale_test.c:30:5: note: include the header <stdlib.h> or explicitly provide a declaration for 'exit' 1 error generated.

Below are the build settings, which were used:
MacOSX11.3.sdk
os=Macos
arch=x86_64
compiler=apple-clang
compiler.version=13
compiler.libcxx=libc++
build_type=Release