GDB/Guile: Don't assert that an integer value is boolean

GDB/Guile: Don't assert that an integer value is boolean

Do not assert that a value intended for an integer parameter, of either
the PARAM_UINTEGER or the PARAM_ZUINTEGER_UNLIMITED type, is boolean,
causing error messages such as:

ERROR: In procedure make-parameter:
ERROR: In procedure gdbscm_make_parameter: Wrong type argument in position 15 (expecting integer or #:unlimited): 3
Error while executing Scheme code.

when initialization with a number is attempted.  Instead assert that it
is integer.  Keep matching `#:unlimited' keyword as an alternative.  Add
suitable test cases.

Approved-By: Simon Marchi <simon.marchi@polymtl.ca>