In mysql/mysql-server@17e497bdb793bc6b8360aa1c626dcd8bb5cfad1b
MySQL 5.6.3 introduced innodb_checksum_algorithm=crc32 and
implemented it for AMD64 using the SSE 4.2 instructions
(incorrectly advertised as "SSE2" in a startup message).
It was not implemented on IA-32 or on Windows.

Since MariaDB 10.2.11 commit 2401d14e
we make use of the SSE4.2 CRC-32C instructions on Windows on both IA-32
and AMD64.

Let us be consistent and implement CRC-32C for IA-32 on all
available platforms. GCC 4.8.2 and GCC 4.8.5 complain
"error: PIC register clobbered by 'ebx' in 'asm'"
so we will only enable this code for IA-32 starting with GCC 5.

Also, we will clean up the implementation further after
commit 1312b4eb.

has_sse4_2(): Replaces ut_cpuid().

ut_crc32c_8(): Replaces ut_crc32_8_hw().

ut_crc32c_64(): Replaces ut_crc32_64_low_hw(), ut_crc32_64_hw().

ut_crc32_hw(): Rewrite.

ut_crc32c_8_sw(): Replaces ut_crc32_8_sw().

ut_crc32c_64_sw(): Replaces ut_crc32_64_low_sw(), ut_crc32_64_sw().

ut_crc32_sw(): Rewrite. Avoid code bloat and do not unroll the
ut_crc32c_64_sw() loop, because no benefit has been demonstrated.

ut_crc32_init(): Only invoke ut_crc32_slice8_table_init()
if no acceleration is available.