Add byacc parser generator

This is meant to replace heirloom yacc for compiling pre-musl parsers.
Unlike heirloom yacc, it's in the public domain, and can be linked with
meslibc without licensing concerns.

steps/byacc-20240109/files/Makefile

@@ -0,0 +1,83 @@
+DEST	      = .
+
+HDRS	      = defs.h
+
+CFLAGS	      ?= -O -DNDEBUG
+
+LDFLAGS	      ?=
+
+LIBS	      ?=
+
+LINKER	      ?= $(CC)
+
+MAKEFILE      = Makefile
+
+OBJS	      = closure.o \
+		error.o graph.o \
+		lalr.o \
+		lr0.o \
+		main.o \
+		mkpar.o mstring.o \
+		output.o \
+		reader.o \
+		symtab.o \
+		verbose.o \
+		warshall.o yaccpar.o
+
+PRINT	      = pr -f -l88
+
+PROGRAM	      = yacc
+
+SRCS	      = closure.c \
+		error.c graph.c \
+		lalr.c \
+		lr0.c \
+		main.c \
+		mkpar.c mstring.c \
+		output.c \
+		reader.c \
+		symtab.c \
+		verbose.c \
+		warshall.c yaccpar.c
+
+all:		$(PROGRAM)
+
+$(PROGRAM):     $(OBJS) $(LIBS)
+		@$(LINKER) $(LDFLAGS) -o $(PROGRAM) $(OBJS) $(LIBS)
+
+clean:;		@rm -f $(OBJS)
+
+clobber:;	@rm -f $(OBJS) $(PROGRAM)
+
+depend:;	@mkmf -f $(MAKEFILE) PROGRAM=$(PROGRAM) DEST=$(DEST)
+
+index:;		@ctags -wx $(HDRS) $(SRCS)
+
+install:	$(PROGRAM)
+		@echo Installing $(PROGRAM) in $(DEST)
+		@install -s $(PROGRAM) $(DEST)
+
+listing:;	@$(PRINT) Makefile $(HDRS) $(SRCS) | lpr
+
+lint:;		@lint $(SRCS)
+
+program:        $(PROGRAM)
+
+tags:           $(HDRS) $(SRCS); @ctags $(HDRS) $(SRCS)
+
+###
+closure.o: defs.h
+error.o: defs.h
+lalr.o: defs.h
+lr0.o: defs.h
+main.o: defs.h
+mkpar.o: defs.h
+output.o: defs.h
+reader.o: defs.h
+symtab.o: defs.h
+verbose.o: defs.h
+warshall.o: defs.h
+btyaccpar.o: defs.h
+yaccpar.o: defs.h
+graph.o: defs.h
+mstring.o: defs.h