Add matching mpfr_clear statements for mpfr_init #144

Job	Run time
build-native-gcc	4m 57s
build-native-llvm	4m 41s
test-native-gcc	8m 35s
test-native-llvm	7m 12s
build-aarch64-gcc	3m 39s
build-aarch64-llvm	2m 53s
build-armhf-gcc	2m 32s
build-armhf-llvm	2m 21s
build-ppc64el-gcc	4m 42s
build-ppc64el-llvm	4m 35s
build-s390x-gcc	1m 58s
build-s390x-llvm	2m 16s
build-riscv64-llvm	2m 48s
test-aarch64-gcc (qemu_cpu: "max,sve=off")	19m 9s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve128=on")	24m 34s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve256=on")	29m 11s
test-aarch64-gcc (qemu_cpu: "max,sve=on,sve512=on")	32m 30s
test-aarch64-llvm (qemu_cpu: "max,sve=off")	17m 38s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve128=on")	22m 23s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve256=on")	25m 33s
test-aarch64-llvm (qemu_cpu: "max,sve=on,sve512=on")	30m 58s
test-armhf-gcc (qemu_cpu: "max")	14m 38s
test-armhf-llvm (qemu_cpu: "max")	13m 32s
test-ppc64el-gcc (qemu_cpu: "power10")	26m 46s
test-ppc64el-llvm (qemu_cpu: "power10")	26m 15s
test-s390x-gcc (qemu_cpu: "")	20m 7s
test-s390x-llvm (qemu_cpu: "")	18m 33s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=false")	12m 33s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=128,elen=64,vext_spec=v1.0")	31m 30s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=256,elen=64,vext_spec=v1.0")	41m 34s
test-riscv64-llvm (qemu_cpu: "rv64,zba=true,zbb=true,zbs=true,v=true,vlen=512,elen=64,vext_spec=v1.0")	1h 1m 6s
	8h 41m 39s

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