Gnu autoheader-2.53

[Deepti Mokkapati]

hi,

I am a novice in GNU...I was using autoheader-2.53..I got the following 
warnings...Could you  please tell me what is the significance of these 
warnings??

warning: do not use m4_patsubst: use patsubst or m4_bpatsubst
configure.in:19: warning: AC_PROG_LEX invoked multiple times
configure.in:69: warning: do not use m4_regexp: use regexp or m4_bregexp
autoheader-2.53: `config.h.in' is unchanged

Thanks
Deepti