Commit 3ed38e42f6 added the POWER8 infrastructure for GCM mode. It also added GCM_SetKeyWithoutResync_VMULL, GCM_Multiply_VMULL and GCM_Reduce_VMULL. This commit adds the remainder, which includes GCM_AuthenticateBlocks_VMULL.
GCC is OK on Linux (ppc64-le) and AIX (ppc64-be). We may need some touchups for XLC compiler
GCM_SetKeyWithoutResync_VMULL, GCM_Multiply_VMULL and GCM_Reduce_VMULL work as expected on Linux (ppc64-le) and AIX (ppc64-be). We are still working on GCM_AuthenticateBlocks_VMULL.
The Crypto++ functions follow IBM's lead and provide VectorLoad, VectorLoadBE, VectorStore, and VectorStoreBE. Additionally, VectorLoadKey was removed in favor of vanilla VectorLoad.
Fix two compilation errors encountered with C++Builder (Starter Edition):
- In `cpu.cpp`, 0ccdc197b introduced a dependency on `_xgetbv()` from `<immintrin.h>` that doesn't exist on C++Builder. Enlist it for the workaround, similar to SunCC in 692ed2a2b.
- In `adv-simd.h`, `<pmmintrin.h>` is being #included under the `CRYPTOPP_SSE2_INTRIN_AVAILABLE` macro. This header, [which apparently provides SSE3 intrinsics](https://stackoverflow.com/a/11228864/1433768), is not shipped with C++Builder. (This section of code was recently downgraded from a SSSE3 to a SSE2 block in 09c8ae28, followed by moving away from `<immintrin.h>` in bc8da71a, followed by reintroducing the SSSE3 check in d1e646a5.) Split the SSE2 and SSSE3 cases such that `<pmmintrin.h>` is not #included for SSE2. This seems safe to do, because some `git grep` analysis shows that:
- `adv-simd.h` is not #included by any other header, but only directly #included by some `.cpp` files.
- Among those `.cpp` files, only `sm4-simd.cpp` has a `CRYPTOPP_SSE2_INTRIN_AVAILABLE` preprocessor block, and there it again includes the other two headers (`<emmintrin.h>` and `<xmmintrin.h>`).
NOTE: I was compiling via the IDE after [setting up a project file](https://github.com/tanzislam/cryptopals/wiki/Importing-into-Embarcadero-C%E2%94%BC%E2%94%BCBuilder-Starter-10.2#using-the-crypto-library). My compilation command was effectively:
```
bcc32c.exe -DCRYPTOPP_NO_CXX11 -DCRYPTOPP_DISABLE_SSSE3 -D__SSE2__ -D__SSE__ -D__MMX__
```
