libc/uClibc: normalize uclibc hidden version names

Hidden version names for uClibc conflicted:

LIBC_UCLIBC_V_0_9_30_2
LIBC_V_0_9_30_1

name them constantly as:
LIBC_UCLIBC_V_<version>

Also update the build script where we use snapshots by version or snapshots by date.

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>

# Blackfin specific configuration file

config ARCH_blackfin

    select ARCH_SUPPORTS_32

    select ARCH_DEFAULT_32

    select ARCH_DEFAULT_LE

    select ARCH_SUPPORT_ARCH

    select ARCH_SUPPORT_CPU

    select ARCH_SUPPORT_TUNE

    select ARCH_SUPPORT_FPU

     help

      The Blackfin architecture