The SoftwareSerial Library of Arduino don't work with clones made of ATMEGA32 as this do not have PCINT feature. How serial communication is linked with PCINT? can the INT pins of ATMEGA32/16 be someway used by the modification of SoftwareSerial.cpp file?
Prior to IDE 1.0.+ the SoftwareSerial used to be a polling of the Rx Pins. This was blockin, requiring constant checking the service of the RX and limited the quality of the baud rate. Since NewSoftSerial replaced the former older Polled SoftwareSerial, using PCint's. Which creates an interrupt on the change of the RX Pin and then checks the time. This is no longer blocking and better emulates the Hardware Serial port, require less (none) servicing (or polling).
One can go back to the older IDE's SoftwareSerial from before 1.+ and attempt to either port it forward or try to use the ATmega32 in the older IDE. I thought I had seen a DEFINE switch somewhere that would allow it to run in polled mode. But I am unable to find it in current releases. Likely did not make it into the released IDE.
Or you can try to find an alternative to SoftwareSerial. Such as tinyserial Where I see that dates back to 2010 and will likely need some updating. Especially on 1.5.8. May have better luck trying it on 1.0.6