pcf: big endian not supported

[armijnhemel]

PCF files can be both little endian and big endian. The specification in KS currently hardcodes that it is little endian, yet doesn't check for big endian files. At least for the Python code this is leading to big memory consumption (because of the way that code for repeatexpr` is generated).

A simple dirty fix would be to disallow big endian files and bail out, the correct way would be to support both.

The simple fix is here:

armijnhemel/binaryanalysis-ng@b00f6ae#diff-07c692af304bcd5effb9469ea4040c5a64432e5ac5706c196f087c23c708e98f