put previously global error handling and key hashes into ptx (pcp context) to make libpcp threadsafe.

src/encryption.h

@@ -36,6 +36,7 @@
 #include "keyhash.h"
 #include "plist.h"
 #include "pcpstream.h"
+#include "context.h"
 
 int pcpdecrypt(char *id, int useid, char *infile, char *outfile, char *passwd, int verify);
 int pcpencrypt(char *id, char *infile, char *outfile, char *passwd, plist_t *recipient, int signcrypt, int armor);