Test t/12placeholders.t fails in 3.8.0 on some architectures

[jplesnik]

I tried to update perl-DBD-pg in Fedora, but the test 12placeholders.t fails on architectures ppc64le, s390x, aarch64, armv7hl. The failure is related to the commit 'Handle backslash-escaped quotes in E'' strings' (dc83d01)

The problem is that char can equal to unsigned char on some architectures. In this case, the assignment char non_standard_strings = -1; can be undefined and the following condition is not evaluated properly.
I fixed it by replacing 'char' with 'signed char'.

[ilmari]

Thanks for the report, fixed in commit 5006a4a.