man: Document that i386 does not suffer performance loss due to PIE anymore

Commit e49be6015dcdcc3ef62ab6bbf58de5053e7dd8ad did not update the
dpkg-buildflags documentation to reflect the fact that at least i386
does not suffer from performance loss due to PIE when using gcc >= 5.

Reported-by: Niels Thykier <niels@thykier.net>

debian/changelog

@@ -128,6 +128,8 @@ dpkg (1.18.5) UNRELEASED; urgency=medium
     - Add list of flags set by bug feature area to dpkg-buildflags(1).
     - Switch output encoding of man pages to UTF-8.
     - Move SEE ALSO section to the end of Dpkg::Changelog::Debian.
+    - Clarify that i386 does not suffer performance loss due to PIE anymore
+      since gcc >= 5 in dpkg-buildflags(1).
 
   [ Updated programs translations ]
   * Dutch (Frans Spiesschaert). Closes: #822797

man/dpkg-buildflags.1

@@ -363,7 +363,8 @@ This is not compatible with \fB\-fPIC\fP so care must be taken when
 building shared objects.
 
 Additionally, since PIE is implemented via a general register, some
-architectures (most notably i386) can see performance losses of up to
+register starved architectures (but not including i386 anymore since
+optimizations implemented in gcc >= 5) can see performance losses of up to
 15% in very text-segment-heavy application workloads; most workloads
 see less than 1%. Architectures with more general registers (e.g. amd64)
 do not see as high a worst-case penalty.