[BDW-GC] "Inlined" storage; `scm_take_' functions

[Ludovic Courtès]

Hello!

Stringbufs and bytevectors are now always "inlined" in the BDW-GC
branch [0, 1], which means that there's no cell->buffer indirection,
which greatly simplifies code (it also takes less room and may slightly
improve performance).

The `scm_take_' functions for strings/symbols/bytevectors are now
essentially aliases to the corresponding `scm_from_' because we cannot
advantageously reuse the provided storage.

Should these functions be deprecated or discouraged?

Thanks,
Ludo'.

[0] 
http://git.savannah.gnu.org/cgit/guile.git/commit/?h=boehm-demers-weiser-gc&id=ba54a2026beaadb4e7566d4b9e2c9e4c7cd793e6
[1] 
http://git.savannah.gnu.org/cgit/guile.git/commit/?h=boehm-demers-weiser-gc&id=0665b3ffcb7ec5232a51ff632a818a638dfd4054