Split up the RSA PKCS#1 encrypt, decrypt, sign and verify functions

Split rsa_pkcs1_encrypt() into rsa_rsaes_oaep_encrypt() and
rsa_rsaes_pkcs1_v15_encrypt()
Split rsa_pkcs1_decrypt() into rsa_rsaes_oaep_decrypt() and
rsa_rsaes_pkcs1_v15_decrypt()
Split rsa_pkcs1_sign() into rsa_rsassa_pss_sign() and
rsa_rsassa_pkcs1_v15_sign()
Split rsa_pkcs1_verify() into rsa_rsassa_pss_verify() and
rsa_rsassa_pkcs1_v15_verify()

The original functions exist as generic wrappers to these functions.
diff --git a/ChangeLog b/ChangeLog
index 2db18e0..605019b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,6 +7,11 @@
      128-bits (found by Yawning Angel)
    * Fixes for 64-bit compilation with MS Visual Studio
 
+Changes
+   * Internally split up rsa_pkcs1_encrypt(), rsa_pkcs1_decrypt(),
+     rsa_pkcs1_sign() and rsa_pkcs1_verify() to separate PKCS#1 v1.5 and
+     PKCS#1 v2.1 functions
+
 Security
    * Removed further timing differences during SSL message decryption in
      ssl_decrypt_buf()