lexer: Be consistent across 32/64 bit in lex_force_int_range().

The exact error message that this function reported varied between 32-
and 64-bit platforms for invalid integers that require more than 32 bits
but no more than 64 bits, since "long int" has a different range between
those platforms.  This commit fixes the problem.

This issue caused the test "testing lexer crash due to overflow" to fail
on 32-bit platforms.

Thanks to Friedrich Beckmann for reporting the problem.