Should fix Windows build again.

Move out-of-class definitions of two methods to hb-static so they
are accessible in libharfbuzz-subset.

This was causing problem on systems without visibility when map was used
from both libharfbuzz and libharfbuzz-subset. Sigh.

https://ci.appveyor.com/project/harfbuzz/harfbuzz/build/1.0.1669/job/dey47nmff0770vp3

Clang build was failing with:

/usr/bin/ld: .libs/libharfbuzz_la-hb-blob.o: relocation R_X86_64_PC32 against undefined hidden symbol `_ZTH12_hb_CrapPool' can not be used when making a shared object

Instead of fighting it, just disable use of it.

Part of fixing https://github.com/behdad/harfbuzz/issues/585

This reverts commit 80af2812, reversing
changes made to c442672e.

This reverts commit c939f6aff405ca7b10b1f1538f46148bff719fcb.