scripts/pem.test:
* add setup for WOLFSSL_NO_DER_TO_PEM,
* exit early with skip code if executable dependencies are missing or WOLFSSL_NO_PEM or NO_CODING, and
* add clean skip clauses to convert_to_pem(), compare_pem(), and pem_der_exp(), if WOLFSSL_NO_DER_TO_PEM.
PEM example converts PEM to DER and DER to PEM.
Supports encrypting DER and writing out as PEM.
Added better support for 40-bit RC2-CBC PBE.
Added AES-128-CBC encryption support with PKCS#5v2.
Fixed handling of iterations to support writing 24-bit values.
Declared enum types for pass to PKCS#8 encryption APIs.
Add more DER and PEM files to certs directory.
Add testing of 'pem' with pem.test script.