Rework mandoc Makefile to ease maintainance

Add compat_reallocarray into libmandoc given other mandoc components will use
it.

lib/libmandoc/Makefile

@@ -27,9 +27,11 @@ LIBROFF_SRCS=	eqn.c \
 		tbl_data.c \
 		tbl_layout.c \
 		tbl_opts.c
+COMPAT_SRCS=	compat_reallocarray.c
 SRCS=		${LIBMAN_SRCS} \
 		${LIBMDOC_SRCS} \
 		${LIBROFF_SRCS} \
+		${COMPAT_SRCS} \
 		chars.c \
 		mandoc.c \
 		mandoc_aux.c \

usr.bin/mandoc/Makefile

@@ -10,11 +10,26 @@ FILESDIR=	${SHAREDIR}/mdocml
 LINKS=	mdocml
 MAN=	mandoc.1 eqn.7 mandoc_char.7 tbl.7 # man.7 mdoc.7 roff.7
 MLINKS= mandoc.1 mdocml.1
-SRCS=	main.c mdoc_term.c chars.c term.c tree.c man_term.c eqn_term.c \
-	mdoc_man.c
-SRCS+=	html.c mdoc_html.c man_html.c out.c eqn_html.c
-SRCS+=	term_ps.c term_ascii.c tbl_term.c tbl_html.c
-SRCS+=	manpath.c compat_reallocarray.c
+
+HTML_SRCS=	eqn_html.c \
+		html.c \
+		man_html.c \
+		mdoc_html.c \
+		tbl_html.c
+MAN_SRCS=	mdoc_man.c
+TERM_SRCS=	eqn_term.c \
+		man_term.c \
+		mdoc_term.c \
+		term.c \
+		term_ascii.c \
+		term_ps.c \
+		tbl_term.c
+SRCS=		${HTML_SRCS} \
+		${MAN_SRCS} \
+		${TERM_SRCS} \
+		main.c \
+		out.c \
+		tree.c
 
 WARNS?=	3
 CFLAGS+= -DHAVE_CONFIG_H