www/c-icap: Fix invalid integer conversion with llvm15+

Fix invalid pointer conversion with llvm15+. This issue
has been corrected previously by asking the compile to ignore
the errors using CFLAGS -Wno-error=int-conversion.
This flag is now removed and the errors properly fixed.

Also fix the some of the paths in the default configuration
to match the FreeBSD HIER.

PR: 271810
Reported by: fluffy