This avoids mistaking symbols with their numeric value when using
certain C preprocessors which output these numeric values at the
beginning of the line as part of an expression.
Seen on OpenBSD 7.5 + clang.
Example `test1167.pl -v` output, before this patch:
```
Source: cpp /home/runner/work/curl/curl/tests/../include/curl/curl.h
Symbol: 20000
Line #3835: 20000 + 142,
[...]
Bad symbols in public header files:
20000
[...]
```
Ref: https://github.com/curl/curl/actions/runs/
9069136530/job/
24918015357#step:3:7513
Ref: #13583
Closes #13634
($_ ne "typedef") &&
($_ ne "enum") &&
($_ ne "=") &&
+ ($_ !~ /^\d+$/) &&
($_ !~ /^[ \t]*$/)) {
if($verbose) {
print "Source: $Cpreprocessor $i$file\n";