Save/restore bound registers in _dl_runtime_resolve
This patch saves and restores bound registers in symbol lookup for x86-64:
1. Branches without BND prefix clear bound registers.
2. x86-64 pass bounds in bound registers as specified in MPX psABI
extension on hjl/mpx/master branch at
https://github.com/hjl-tools/x86-64-psABI
https://groups.google.com/forum/#!topic/x86-64-abi/KFsB0XTgWYc
Binutils has been updated to create an alternate PLT to add BND prefix
when branching to ld.so.
* config.h.in (HAVE_MPX_SUPPORT): New #undef.
* sysdeps/x86_64/configure.ac: Set HAVE_MPX_SUPPORT.
* sysdeps/x86_64/configure: Regenerated.
* sysdeps/x86_64/dl-trampoline.S (REGISTER_SAVE_AREA): New
macro.
(REGISTER_SAVE_RAX): Likewise.
(REGISTER_SAVE_RCX): Likewise.
(REGISTER_SAVE_RDX): Likewise.
(REGISTER_SAVE_RSI): Likewise.
(REGISTER_SAVE_RDI): Likewise.
(REGISTER_SAVE_R8): Likewise.
(REGISTER_SAVE_R9): Likewise.
(REGISTER_SAVE_BND0): Likewise.
(REGISTER_SAVE_BND1): Likewise.
(REGISTER_SAVE_BND2): Likewise.
(_dl_runtime_resolve): Use them. Save and restore Intel MPX
bound registers when calling _dl_fixup.