shells: make hush test optional, rename ASH_BUILTIN_foo -> ASH_foo

This makes hash and ash more symmetrical wrt config menu and config
options.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/configs/TEST_rh9_defconfig b/configs/TEST_rh9_defconfig
index 4a5fad3..86e13cd 100644
--- a/configs/TEST_rh9_defconfig
+++ b/configs/TEST_rh9_defconfig
@@ -893,9 +893,9 @@
 CONFIG_ASH_JOB_CONTROL=y
 CONFIG_ASH_ALIAS=y
 CONFIG_ASH_GETOPTS=y
-CONFIG_ASH_BUILTIN_ECHO=y
-CONFIG_ASH_BUILTIN_PRINTF=y
-CONFIG_ASH_BUILTIN_TEST=y
+CONFIG_ASH_ECHO=y
+CONFIG_ASH_PRINTF=y
+CONFIG_ASH_TEST=y
 CONFIG_ASH_CMDCMD=y
 # CONFIG_ASH_MAIL is not set
 CONFIG_ASH_OPTIMIZE_FOR_SIZE=y