Build: Makefile.am f.: move/drop comments to reflect previous commits

• "# lex/yacc issues":
• introduced with 800b0c3 ("CFLAGS = $(CFLAGS_COPY:-Werror=)")
• comment + the statement got separated as of ae6fb13

• "# utils.h pengine.h"
• introduced with a4d9634
• became superfluous as of ef1f2e2