Hmm. I also had some problems compiling
RTMPdump. But it seems to me that your polarssl installation is not correct. For example "ssl_default_ciphers" is a function that should be in here: "C:\MinGW\include\polarssl\ssl.h"
Maybe this command "make DESTDIR=/MinGW install" (copies files into the root directory of your MinGW installation) failed.
Verify that these directories do exit:
C:\MinGW\include\polarssl\*some_polarssl_files*
C:\MinGW\bin\*some_polarssl_files*
C:\MinGW\lib\libpolarssl.a
Btw, I also could only compile RTMPDump in this constellation:
mingw-get-inst-20110530.exe
-Use pre-packaged repository catalogues
-Selected: MinGW Developer Kit (includes Perl)
polarssl-0.14.3-gpl.tgz