Removes some swig workaround code put in for ticket 181.

This seems to fix the import problems recently seen on 12.10 for loading gnuradio-companion (due to 'from lxml import etree' which was actually due to 'import os' causing a segfault).
analog: adding squelch_base_ff and ctcss_squelch_ff to analog.

This addresses the issues of inheriting from both gr_block and another block (squelch_base_ff, in this case).
analog: adding complex squelch base class.
analog: implemented all AGC classes in gr-analog with QA code.
analog: added cpfsk to gr-analog.
analog: adding dpll_bb to gr-analog.
analog: adding GRC blocks for:

- AGC
- AGC2
- Feedforward AGC
- CPFSK
- CTCSS squelch
- DPLL
analog: added fmdet block to gr-analog.
analog: adding frequency_modulator_fc to gr-analog, with QA and GRC.
core: update to build_utils to help with '_i_impl' blocks.
analog: adding noise_source to gr-analog with GRC and QA.
analog: adding phase_modulator_fc to gr-analog with QA and GRC.
analog: fixing noise source in GRC.
analog: added PLL blocks to gr-analog with QA and GRC.
analog: adding probe_avg_mag_sqrd blocks to gr-analog with QA and GRC.
analog: moving LFSR code into gr-analog.
core: adding int32_t and uint32_t types to swig.
analog: export lfsr class to Python and adding QA code for it.
analog: executable flag for python QA codes.
digital: switched digital components over to using LFSR class now in gr-analog.