Log Message:
libgcrypt: update to 1.9.1.

Comment out some old workarounds for configure script/compiler issues,
and trust the upstream configure script again until proven wrong.

Remove hacks.mk, the grep does not match anything any longer.

Noteworthy changes in version 1.9.1 (2021-01-29)  [C23/A3/R1]
------------------------------------------------

 * Bug fixes:

   - Fix exploitable bug in hash functions introduced with 1.9.0.
     [#5275]

   - Return an error if a negative MPI is used with sexp scan
     functions.  [#4964]

   - Check for operational FIPS in the random and KDF functions.
     [#5243]

   - Fix compile error on ARMv7 with NEON disabled.  [#5251]

   - Fix self-test in KDF module.  [#5254]

   - Improve assembler checks for better LTO support.  [#5255]

   - Fix assember problem on macOS running on M1.  [#5157]

   - Support older macOS without posix_spawn. [#5159]

   - Fix 32-bit cross build on x86.  [#5257]

   - Fix non-NEON ARM assembly implementation for SHA512.  [#5263]

   - Fix build problems with the cipher_bulk_ops_t typedef.  [#5264]

   - Fix Ed25519 private key handling for preceding ZEROs. [#5267]

   - Fix overflow in modular inverse implementation.  [#5269]

   - Fix register access for AVX/AVX2 implementations of Blake2.
     [#5271].

 * Performance:

   - Add optimized cipher and hash functions for s390x/zSeries.

   - Use hardware bit counting functionx when available.

 * Internal changes:

   - The macOS getentropy syscall is used when available.  [#5268]

   - Update DSA functions to match FIPS 186-3.  [30ed9593f6]

   - New self-tests for CMACs and KDFs.  [385a89e35b,7a0da24925]

   - Add bulk cipher functions for OFB and GCM modes.
     [f12b6788f2,f4e63e92dc]

 Release-info: https://dev.gnupg.org/T5259