When compiled with enforced ISO C (e.g. -std=c11) 'asm' inline
does not compile (it's GNU extension). Use __asm__ inline assembly
with GCC and clang compliers instead.
Fixes: #786.
Starting with GCC10 and LTO enabled, current symbols
versioning hack does not work anymore. This patch
reflects on that and should be compatible with older
compilers that does not support __attribute__((symver))
yet.
Inspired by following code:
https://github.com/linux-rdma/rdma-core/blob/master/util/symver.h