Lua replace fscanf

Rocklua was using the full fscanf implementation
to simply read %ld for the file:read("*n") function
wasting 1k on unneeded/unused functionality

Instead, I've implemented a filetol function to duplicate it
without the extra overhead using strtol which as an added bonus
ERANGE errors now resolve to LONG_MIN and LONGMAX instead of
integer overflow

filetol()
   reads long int from an open file, skips preceding
   whitespaces returns -1 if error, 1 on success.
   *num set to LONG_MAX or LONG_MIN on overflow.
   If number of digits is > than LUAI_MAXNUMBER2STR
   filepointer will continue till the next non digit
   but buffer will stop being filled with characters.
   Preceding zero is ignored.

Change-Id: Ia42d0f73c63a894625bca4581e9b7e1cc7387fd2

apps/plugins/lua/rocklib.h

@@ -47,6 +47,7 @@ struct lua_str_reg {
 
 LUALIB_API int (luaopen_rock) (lua_State *L);
 int get_current_path(lua_State *L, int level);
+int filetol(int fd, long *num);
 
 #endif /* _ROCKLIB_H_ */