First-level of support for new aarch64 machines

Testing on Neoverse N1 (Ampere 3GHz). Tested only on a subset of phy-simulators.

- Changes:
- use SIMDE consistently
- adaptations of LDPC decoder generator for ARMv8 performance
- SIMDe modifications of Intel CRC to allow for aarch64 build.
  optimizations for 128-bit to improve performance of LDPC encode/decode
  on aarch64 (Neoverse 1)
- added BG2 files for 128-bit ldpc encoder (aarch64)
- testing on Xeon
- testing on x86
- minor changes to build/run on x86
- change in crc.h after returning to aarch64
- removed some warning in ldpc decoder generator for x86_64
- char
- Delete irrelevant constants
- Correctly declare variables
- Define stdbool for all architectures
- Remove definition of _MM_SHUFFLE and use SIMDE_MM_SHUFFLE
- Remove commented code
- Fix CMakeLists.txt
- Include SIMDE avx2 functions in tools_defs.h

openair1/PHY/CODING/nrLDPC_encoder/ldpc_encoder_optim.c

@@ -99,7 +99,7 @@ int nrLDPC_encod(unsigned char **test_input,unsigned char **channel_input,int Zc
 
   if(impp->tinput != NULL) stop_meas(impp->tinput);
 
-  if ((BG==1 && Zc>176) || (BG==2 && Zc>64)) { 
+  if ((BG==1 && Zc>=176) || (BG==2 && Zc>=64)) { 
     // extend matrix
     if(impp->tprep != NULL) start_meas(impp->tprep);
     if(impp->tprep != NULL) stop_meas(impp->tprep);