BuildSystem: Move all userpace libraries under the userspace directory

As the number of libraries is increasing, root directory starts to
expand. This adds better organization for libraries

userspace/libraries/LibC/include/stdlib.h

@@ -0,0 +1,112 @@
+#ifndef _STDLIB_H
+#define _STDLIB_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stdlib.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#include <limits.h>
+#include <math.h>
+#include <sys/wait.h>
+
+#define __need_NULL
+#define __need_size_t
+#define __need_wchar_t
+#include <stddef.h>
+
+#define EXIT_FAILURE 1
+#define EXIT_SUCCESS 0
+
+#define RAND_MAX INT32_MAX
+
+#define MB_CUR_MAX ((size_t)4)
+
+typedef struct
+{
+	int quot;	/* quotient */
+	int rem;	/* remainder */
+} div_t;
+
+typedef struct
+{
+	long quot;	/* quotient */
+	long rem;	/* remainder */
+} ldiv_t;
+
+typedef struct
+{
+	long long quot;	/* quotient */
+	long long rem;	/* remainder */
+} lldiv_t;
+
+void				_Exit(int status) __attribute__((__noreturn__));
+long				a64l(const char* s);
+void				abort(void) __attribute__((__noreturn__));
+int					abs(int i);
+int					atexit(void (*func)(void));
+double				atof(const char* str);
+int					atoi(const char* str);
+long				atol(const char* str);
+long long			atoll(const char* str);
+void*				bsearch(const void* key, const void* base, size_t nel, size_t width, int (*compar)(const void*, const void*));
+void*				calloc(size_t nelem, size_t elsize);
+div_t				div(int numer, int denom);
+double				drand48(void);
+double				erand48(unsigned short xsubi[3]);
+void				exit(int status);
+void				free(void* ptr);
+char*				getenv(const char* name);
+int					getsubopt(char** optionp, char* const* keylistp, char** valuep);
+int					grantpt(int fildes);
+char*				initstate(unsigned seed, char* state, size_t size);
+long				jrand48(unsigned short xsubi[3]);
+char*				l64a(long value);
+long				labs(long i);
+void				lcong48(unsigned short param[7]);
+ldiv_t				ldiv(long numer, long denom);
+long long			llabs(long long i);
+lldiv_t				lldiv(long long numer, long long denom);
+long				lrand48(void);
+void*				malloc(size_t size);
+int					mblen(const char* s, size_t n);
+size_t				mbstowcs(wchar_t* __restrict pwcs, const char* __restrict s, size_t n);
+int					mbtowc(wchar_t* __restrict pwc, const char* __restrict s, size_t n);
+char*				mkdtemp(char* _template);
+int					mkstemp(char* _template);
+long				mrand48(void);
+long				nrand48(unsigned short xsubi[3]);
+int					posix_memalign(void** memptr, size_t alignment, size_t size);
+int					posix_openpt(int oflag);
+char*				ptsname(int fildes);
+int					putenv(char* string);
+void				qsort(void* base, size_t nel, size_t width, int (*compar)(const void*, const void*));
+int					rand(void);
+int					rand_r(unsigned* seed);
+long				random(void);
+void*				realloc(void* ptr, size_t size);
+char*				realpath(const char* __restrict file_name, char* __restrict resolved_name);
+unsigned short*		seed48(unsigned short seed16v[3]);
+int					setenv(const char* envname, const char* envval, int overwrite);
+void				setkey(const char* key);
+char*				setstate(char* state);
+void				srand(unsigned seed);
+void				srand48(long seedval);
+void				srandom(unsigned seed);
+double				strtod(const char* __restrict nptr, char** __restrict endptr);
+float				strtof(const char* __restrict nptr, char** __restrict endptr);
+long				strtol(const char* __restrict nptr, char** __restrict endptr, int base);
+long double			strtold(const char* __restrict nptr, char** __restrict endptr);
+long long			strtoll(const char* __restrict nptr, char** __restrict endptr, int base);
+unsigned long		strtoul(const char* __restrict nptr, char** __restrict endptr, int base);
+unsigned long long	strtoull(const char* __restrict nptr, char** __restrict endptr, int base);
+int					system(const char* command);
+int					unlockpt(int fildes);
+int					unsetenv(const char* name);
+size_t				wcstombs(char* __restrict s, const wchar_t* __restrict pwcs, size_t n);
+int					wctomb(char* s, wchar_t wchar);
+
+__END_DECLS
+
+#endif