Use -Wall and -Werror.
Remove unused variable.
Fix use of uninitialized values.
Use -pedantic.
Forget -Werror for now.
Fix variadic macro warning.

  extsmail.c:91:33: warning: ISO C does not permit named variadic macros [-Wvariadic-macros]
  #   define SPOOL_WRITE(fmt, args...) if (fprintf(sf, fmt, ##args) == -1) \