volk: cleaned up 32fc_x2_dot_prod_32fc code. Improved results; fixed on OS X.

- Added unaligned versions of kernels.
- Fixed issues with tail handling
- Use _mm_setzero_ps instead of subtracting to zero out values
volk: fixed issue with size_t comparison of std::string function (compare against std::npos, not -1).
Merge branch 'maint'
Merge branch 'master' into next
Revert "GNU Radio EXPAND macros for template files:"

This reverts commit 6fc200fcba65cc4d18d7b10381da72769c0183c4.

The original commit causes excessive rebuild sensitivity by
regenerating many public API header files at cmake time instead
of at build time.
Merge branch 'master' into next