Add some missing libc functions: setenv, unsetenv, strdup.

--HG--
branch : dtrg-videocore
rename : lang/cem/libcc.ansi/stdlib/getenv.c => lang/cem/libcc.ansi/stdlib/setenv.c
rename : lang/cem/libcc.ansi/string/strlen.c => lang/cem/libcc.ansi/string/strdup.c

lang/cem/libcc.ansi/headers/string.h

@@ -33,5 +33,8 @@ extern char	*strtok(char *_s1, const char *_s2);
 extern void	*memset(void *_s, int _c, size_t _n);
 extern char	*strerror(int _errnum);
 extern size_t	strlen(const char *_s);
+extern char *strdup(const char *_s);
+
+#define bcopy(s, d, z) memmove(d, s, z)
 
 #endif