Tricore: add a FCALL calling convention

[esaulenka]

While working with tricore binary I found that some small routines can be called through FCALL (fast call) opcode, not by common CALL.
And even though it is already supported in sleigh, it produces a wrong decompiled code if caller function uses stack variables, because CALL and FCALL handle stack in a different manner.

So, here is two patches:

• add a new calling convention to support these functions
• copy of the HCS12 plugin to automatically detect such functions.

some notes:

• I'm not sure that the FCALL can be used in the C++ code (to be honest, I have never seen C++ tricore binaries)
• I'm not sure about parameters transferred through stack. For common functions it working good enough, but my sample use the only few fast calls with just a few arguments, there is no stack usage to transfer parameters.