Implement GCC visibility support

[ethanmusser]

Implement GCC visibility support as part of the MULTISENSE_API macro.

Relevant Code

LibMultiSense/source/LibMultiSense/include/MultiSense/MultiSenseTypes.hh

Lines 54 to 66 in 3822681

	#if !defined(MULTISENSE_API)
	# if defined (_MSC_VER)
	# if defined (MultiSense_STATIC)
	# define MULTISENSE_API
	# elif defined (MultiSense_EXPORTS)
	# define MULTISENSE_API __declspec(dllexport)
	# else
	# define MULTISENSE_API __declspec(dllimport)
	# endif
	# else
	# define MULTISENSE_API
	# endif
	#endif

Original Comment (@jmonticelli)

GNU has visibility support, and if done tastefully, can be of great benefit -- though I don't believe you need it by default.

https://gcc.gnu.org/wiki/Visibility

That link not only shows how the feature can be useful, but shows the inverse optimization, which this library doesn't support, but could in the future.

Guaranteed to increase complexity, but worth being aware of regardless, even if this is something we punt on now.

Originally posted by @jmonticelli in #296 (comment)