Don't attempt to use copy relocs for TLS
Relax TLS sequences in executables

Sequences to address thread-local variables like

  lui  v0, %tprel_hi(my_tls_var)
  add  v0, v0, tp
  addi v0, v0, %tprel_lo(my_tls_var)

can now be relaxed to

  addi v0, tp, %tprel_lo(my_tls_var)

when the thread pointer offset fits in 12 bits.
Relax TLS IE to TLS LE when legal
Speed up relocation processing