libutil: remove sds string library

The sds string library included in libutil is no longer used by
anything in flux-core. Remove it.

Fixes #3133

Makefile.am

@@ -25,7 +25,6 @@ CODE_COVERAGE_IGNORE_PATTERN = \
 	"/usr/lib*" \
 	"*/bindings/python/*" \
 	"*/common/liblsd/*" \
-	"*/common/libutil/sds.*" \
 	"*/common/liboptparse/getopt*" \
 	"*/common/libtestutil/*" \
 	"*/common/libyuarel/*"

codecov.yml

@@ -12,7 +12,6 @@ coverage:
  - ".*/common/libtomlc99/.*"
  - ".*/common/liboptparse/getopt*"
  - ".*/bindings/python/.*.c"
- - ".*/common/libutil/sds.*"
  - ".*/common/libminilzo/.*"
  - "/usr/include/.*"
  - "/usr/lib/.*"

src/common/libutil/Makefile.am

@@ -42,9 +42,6 @@ libutil_la_SOURCES = \
 	cleanup.h \
 	unlink_recursive.c \
 	unlink_recursive.h \
-	sds.c \
-	sds.h \
-	sdsalloc.h \
 	iterators.h \
 	macros.h \
 	sha1.h \