clover: Add constructor for constant_argument.

Fix defects reported by Coverity Scan.

member_not_init_in_gen_ctor: The compiler-generated constructor for this class does not initialize buf.
member_not_init_in_gen_ctor: The compiler-generated constructor for this class does not initialize st.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <!10399>
34 jobs for !10399 with fix-cid-1213938 in 9 minutes and 24 seconds (queued for 5 seconds)
latest detached
Status Job ID Name Coverage
  Sanity
passed #9302292
sanity

00:00:09

 
  Container
passed #9302295
aarch64
arm_build

00:00:18

passed #9302296
windows shell 1809 mesa
windows_build_vs2019

00:00:09

passed #9302293
x86_build-base

00:00:20

passed #9302294
x86_test-base

00:00:21

 
  Container 2
passed #9302301
android_build

00:00:14

passed #9302298
i386_build

00:00:20

passed #9302304
kernel+rootfs_amd64

00:01:19

passed #9302305
aarch64
kernel+rootfs_arm64

00:01:13

passed #9302306
aarch64
kernel+rootfs_armhf

00:00:11

passed #9302299
ppc64el_build

00:00:20

passed #9302300
s390x_build

00:00:15

passed #9302297
x86_build

00:00:20

passed #9302302
x86_test-gl

00:00:15

passed #9302303
x86_test-vk

00:00:14

 
  Meson X86 64
passed #9302312
meson-clang

00:08:30

passed #9302313
meson-clover

00:01:40

passed #9302309
meson-clover-testing

00:01:17

passed #9302310
meson-gallium

00:04:22

passed #9302311
meson-release

00:02:54

passed #9302307
meson-testing

00:01:41

passed #9302308
meson-testing-asan

00:02:13

passed #9302314
meson-vulkan

00:01:42

 
  Build Misc
passed #9302315
arm_test

00:00:40

passed #9302316
meson-android

00:01:21

passed #9302318
aarch64
meson-arm64

00:01:35

passed #9302319
aarch64
meson-arm64-asan

00:03:34

passed #9302320
aarch64
meson-arm64-build-test

00:01:23

passed #9302317
aarch64
meson-armhf

00:01:36

passed #9302321
meson-i386

00:01:40

passed #9302324
meson-mingw32-x86_64

00:01:46

passed #9302323
meson-ppc64el

00:03:20

passed #9302322
kvm
meson-s390x

00:03:14

 
  Software Renderer
passed #9302325
llvmpipe-piglit-cl

00:01:35