bindings: add u32/SR_T_UINT32 support for config keys

Previous bindings for C++ and other languages lacked support for the
uint32_t data type for config keys. Which terminated the program with
the message:

  Exception: internal error

The following PulseView commands reproduced the issue:

  $ pulseview -i /dev/null -I csv:single_column=1
  $ pulseview -i /dev/null -I csv:first_column=1
  $ pulseview -i /dev/null -I csv:logic_channels=1
  $ pulseview -i /dev/null -I csv:start_line=1

  $ pulseview -i /dev/null -I saleae:wordsize=1
  $ pulseview -i /dev/null -I saleae:logic_channels=1

  $ pulseview -i /dev/null -I vcd:numchannels=1

Add support for uint32_t data types in the C++, Python, and Ruby
language bindings.

[ gsi: separate stou32() helper ]