build: use dnl for comments in configure.ac
build: use dnl for comments in configure.ac

This simply means the comments are not copied into the executed
configure script.

lyx2014/-opencore-amr,yxl/opencore-amr-js,BelledonneCommunications/opencore-amr,yxl/opencore-amr-js,jiangjianping/opencore-amr,jiangjianping/opencore-amr,yxl/opencore-amr-js,yxl/opencore-amr-js,lyx2014/-opencore-amr,BelledonneCommunications/opencore-amr,yxl/opencore-amr-js