PR target/44218, improve -mrecip on powerpc

gcc/ChangeLog

gcc/config/rs6000/altivec.h

gcc/config/rs6000/altivec.md

gcc/config/rs6000/rs6000-builtin.def

gcc/config/rs6000/rs6000-c.c

gcc/config/rs6000/rs6000-protos.h

gcc/config/rs6000/rs6000.c

gcc/config/rs6000/rs6000.h

gcc/config/rs6000/rs6000.md

gcc/config/rs6000/rs6000.opt

gcc/config/rs6000/vector.md

gcc/config/rs6000/vsx.md

gcc/doc/extend.texi

gcc/doc/invoke.texi

gcc/testsuite/ChangeLog

gcc/testsuite/gcc.target/powerpc/recip-1.c

gcc/testsuite/gcc.target/powerpc/recip-2.c

gcc/testsuite/gcc.target/powerpc/recip-3.c

gcc/testsuite/gcc.target/powerpc/recip-4.c

gcc/testsuite/gcc.target/powerpc/recip-5.c