Revert GCC change about turning -Wimplicit-function-declaration into … #78

Job	Run time
Native build	5s
Cross build (ia64-unknown-linux-gnu)	27m 28s
Cross build (alpha-unknown-linux-gnu)	22m 50s
Cross build (x86_64-unknown-linux-gnu)	24m 19s
Cross build (i386-unknown-linux-gnu)	23m 54s
Cross build (arm-unknown-linux-gnueabi)	25m 6s
Cross build (arm-unknown-linux-gnueabihf)	24m 47s
Cross build (hppa-unknown-linux-gnu)	23m 30s
Cross build (aarch64-unknown-linux-gnu)	27m 5s
Cross build (mips-unknown-linux-gnu)	26m 58s
Cross build (mipsel-unknown-linux-gnu)	24m 22s
Cross build (powerpc-unknown-linux-gnu)	26m 19s
Cross build (s390-unknown-linux-gnu)	23m 44s
Cross build (s390x-unknown-linux-gnu)	23m 52s
Cross build (sparc-unknown-linux-gnu)	25m 8s
Cross build (powerpc64le-unknown-linux-gnu)	25m 20s
Cross build (mips64el-unknown-linux-gnuabi64)	24m 52s
	6h 39m 39s

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