#3 patch for making ruby-gsl work with multiple versions of gsl

[Paul Brannan]

Attached is patch to get ruby-gsl to compile with
gsl-1.1.1 (and 1.2 and 1.3 and 1.4, though I didn't
test those). I just #if'd out the parts that weren't
implemented when that version of gsl was written.

Also, I changed the include guards in your header
files; identifiers beginning with an underscore and
followed by a capital letter are reserved and should
not be used (section 7.1.3 in the C standard).

[Paul Brannan]