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>

 # m68k specific configuration file

 # depends on EXPERIMENTAL

 config ARCH_m68k

     select ARCH_SUPPORTS_32

     select ARCH_DEFAULT_32

     select ARCH_DEFAULT_BE

     select ARCH_SUPPORT_CPU

      help

       The m68k architecture