Make text appear in GUI console, Zip install works.

Move TW zip install code to C++ so that it can use the
ui->functions.
Bring in mincrypt code to fix a crash during signature
checking.

install.cpp

@@ -46,7 +46,7 @@ static const float DEFAULT_FILES_PROGRESS_FRACTION = 0.4;
 static const float DEFAULT_IMAGE_PROGRESS_FRACTION = 0.1;
 
 // If the package contains an update binary, extract it and run it.
-extern "C" int
+static int
 try_update_binary(const char *path, ZipArchive *zip, int* wipe_cache) {
     const ZipEntry* binary_entry =
             mzFindZipEntry(zip, ASSUMED_UPDATE_BINARY_NAME);