build: Use the right autoconf checks for the compiler
build: Use the right autoconf checks for the compiler

 * AM_PROG_CC_C_O has been replaced by the AC_PROG_CC_C_O macro
 * AC_PROG_CC_C99 is the portable macro for checking that the
   compiler supports C99, and for exporting the proper compiler
   flags for C99

[endlessm/eos-sdk#1298]

endlessm/eos-metrics,endlessm/eos-metrics,endlessm/eos-metrics,endlessm/eos-metrics,endlessm/eos-metrics,endlessm/eos-metrics