glcpp: Generate an error for division by zero
When GCC encounters a division by zero in a preprocessor directive, it
generates an error. Since the GLSL spec says that the GLSL
preprocessor behaves like the C preprocessor, we should generate that
same error.
It's worth noting that I cannot find any text in the C99 spec that
says this should be an error. The only text that I can find is line 5
on page 82 (section 6.5.5 Multiplicative Opertors), which says,
"The result of the / operator is the quotient from the division of
the first operand by the second; the result of the % operator is
the remainder. In both operations, if the value of the second
operand is zero, the behavior is undefined."
Fixes 093-divide-by-zero.c test and bugzilla #32831.
NOTE: This is a candidate for the 7.9 and 7.10 branches.