lalsuite_build.m4: add LALSUITE_VERSION_COMPARE() macro

- more intuitive wrapper around AS_VERSION_COMPARE() macro
SWIG: allow SWIG minimum required version to be modified per language

- in particular, Octave v3.8.0 or later requires SWIG v2.0.12 or later
lalsuite_build.m4, lalsuite_swig.m4: style cleanup of AS_CASE() macros

- Remove unneeded [*], since last argument already uses default pattern
added SimInspiralGetFrequency to return frequency for various functions; also added a wrapper function to get frequency at the SEOBNR peak amplitude