Update to Guile 1.8.8

Changes in 1.8.8 (since 1.8.7)

* Bugs fixed

** Fix possible buffer overruns when parsing numbers
** Fix random number generator on 64-bit platforms

Previously the `scm_c_random' function would crash or return only 32-bit
worth of randomness.  In addition, the new `scm_c_random64' function
explicitly returns 64 bits of randomness.

** Add missing range checks in `vector-move-left!' and `vector-move-right!'

Previously these procedures could write past the end of a vector.

** Avoid clash with system setjmp/longjmp on IA64
** Don't dynamically link an extension that is already registered
** Fix `wrong type arg' exceptions with IPv6 addresses
** Fix typos in `(srfi srfi-19)'
** Have `(srfi srfi-35)' provide named struct vtables
** Fix C documentation extraction ("snarfing") with recent GCC versions
** Fix some Interix build problems
** Fix Tru64 build problems
** Fix GC-related build issues on Solaris 10 x86 with Sun Studio 12
** Several small documentation fixes

(asau)