5798 fexecve() needed per POSIX 2008

*** 421,430 ****
--- 421,433 ----
  int fattach(int fildes, const char *path);
  
  /* fdetach.c */
  int fdetach(const char *path);
  
+ /* fexecve.c */
+ int fexecve(int, char *const argv[], char *const envp[]);
+ 
  /* ffs.c */
  int ffs(int field);
  
  /* fmtmsg.c */
  int addseverity(int value, const char *string);