Revert "Mutex call in x509_crt.c depended on PTHREAD specific instead of generic"

This reverts commit 9eae7aae80c5e9c7a6b798b3930e00b53c063604.
Revert "Merged RSA-PSS support in Certificate, CSR and CRL"

This reverts commit ab50d8d30c22f38e3e2d2373219cfbeb1940082e, reversing
changes made to e31b1d992ad0a3874646c73a44f3eb750d13e900.
Fix verion-major intolerance
Print protocol version in example cli/srv
Fxi typo
Fix forgotten curves in #ifdef
Add -Wunreachable-code to check mode

See eg https://www.imperialviolet.org/2014/02/22/applebug.html
Fixed CMake symlinking on out-of-source builds
Avoid "unreachable code" warning
Countermeasure against "triple handshake" attack
Fix error code in dhm_selftest()
Add missing #ifdefs in aes.h
Fix depend issues in test suites for cipher modes
Add x509_time_future()
Reject certs and CRLs from the future
Avoid possible segfault on bad server ciphersuite
Forbid sequence number wrapping
Fix RSASSA-PSS example programs
Fix more depend issues on specific curves
Reserve -1 as an error code (used in programs)