Split fs.c file

+ Misc changes to code in io.c

source/tegraexplorer/fs.h

@@ -45,6 +45,4 @@ enum foldermenuoptions {
 
 int readfolder(const char *path);
 void fileexplorer(const char *startpath);
-bool checkfile(char* path);
-u64 getfilesize(char *path);
-int copy(const char *locin, const char *locout, bool print, bool canCancel);
+char *getnextloc(char *current, char *add);