Commit (HEAD): peer libiconv no longer required on win32 (divingmake), still default

[Mark Gilbert]

You have to explicitly set ABI_REQUIRE_PEER_LIBICONV=0 to not use peer. 
Before, it was impossible to not use peer (within the limits of not
hacking the build system *g*).
Mingw project provides a darn fine libiconv.

-MG