Add Solaris specific declararions for dlfcn.

Add definitions to `core.sys.posix.dlfcn` and add new `modul core.sys.solaris.dlfcn`.
Why not simply adding them?
I just found [this](https://searchcode.com/codesearch/view/5447099/), an official repo would be preferred though.
```c
typedef struct	dl_argsinfo {
	long		dla_argc;	/* process argument count */
	char		**dla_argv;	/* process arguments */
	char		**dla_envp;	/* process environment variables */
	auxv_t		*dla_auxv;	/* process auxv vectors */
} Dl_argsinfo;
typedef	Dl_argsinfo	Dl_argsinfo_t;

typedef struct {
	mmapobj_result_t *dlm_maps;	/* mapping information */
	uint_t		dlm_acnt;	/* number of dlm_maps mappings */
	uint_t		dlm_rcnt;	/* number of returned mappings */
} Dl_mapinfo_t;

typedef struct {
	uint_t		dlui_version;	/* version # */
	uint_t		dlui_flags;	/* flags */
	char		*dlui_objname;	/* path to object */
	void		*dlui_unwindstart; /* star of unwind hdr */
	void		*dlui_unwindend; /* end of unwind hdr */
	void		*dlui_segstart;	/* start of segment described */
					/*  by unwind block */
	void		*dlui_segend;	/* end of segment described */
					/*  by unwind block */
} Dl_amd64_unwindinfo;
typedef	Dl_amd64_unwindinfo	Dl_amd64_unwindinfo_t;
```