feat(userspace/libc): implement functions for porting apps

Signed-off-by: EnderIce2 <enderice2@protonmail.com>

Userspace/libc/include/iconv.h

@@ -0,0 +1,29 @@
+/*
+	This file is part of Fennix C Library.
+
+	Fennix C Library is free software: you can redistribute it and/or
+	modify it under the terms of the GNU General Public License as
+	published by the Free Software Foundation, either version 3 of
+	the License, or (at your option) any later version.
+
+	Fennix C Library is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Fennix C Library. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#ifndef _ICONV_H
+#define _ICONV_H
+
+#include <stddef.h>
+
+typedef void *iconv_t;
+
+iconv_t iconv_open(const char *tocode, const char *fromcode);
+size_t iconv(iconv_t cd, char **restrict inbuf, size_t *restrict inbytesleft, char **restrict outbuf, size_t *restrict outbytesleft);
+int iconv_close(iconv_t cd);
+
+#endif // _ICONV_H