Implement fcvtmu x_d.  Fixes #339927.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2982 8f6e269a-dfd6-0310-a8e1-e2731360e62c
Implement
FMLA 2d_2d_d[], 4s_4s_s[], 2s_2s_s[]
FMLS 2d_2d_d[], 4s_4s_s[], 2s_2s_s[]
Fixes #339938 and its dup, #339950.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2983 8f6e269a-dfd6-0310-a8e1-e2731360e62c