Chunk 1:	Change PREFIX and MANPREFIX variables
Chunk 2:	Append local (C|CXX|LD)FLAGS, change _BSD_SOURCE define
		to _DEFAULT_SOURCE
diff -ura sfeed.orig/config.mk sfeed.new/config.mk
--- sfeed.orig/config.mk	2019-01-18 00:18:57.872915214 +1100
+++ sfeed.new/config.mk	2019-01-18 00:19:40.113859873 +1100
@@ -1,8 +1,8 @@
 # customize below to fit your system
 
 # paths
-PREFIX = /usr/local
-MANPREFIX = ${PREFIX}/man
+PREFIX = /usr
+MANPREFIX = ${PREFIX}/share/man
 
 # compiler and linker
 CC = cc
diff -ura sfeed.orig/config.mk sfeed.new/config.mk
--- sfeed.orig/config.mk	2019-01-17 23:01:44.402627527 +1100
+++ sfeed.new/config.mk	2019-01-17 23:14:29.356401258 +1100
@@ -14,11 +14,11 @@
 #LDFLAGS =

 # optimized
-CFLAGS = -O2 -std=c99
-LDFLAGS = -s
+CFLAGS  += -O2 -std=c99
+LDFLAGS += -s
 
 # optimized static
 #CFLAGS = -static -O2 -std=c99
 #LDFLAGS = -static -s
 
-CPPFLAGS = -D_POSIX_C_SOURCE=200809L -D_XOPEN_SOURCE=700 -D_BSD_SOURCE
+CPPFLAGS += -D_POSIX_C_SOURCE=200809L -D_XOPEN_SOURCE=700 -D_DEFAULT_SOURCE