Recommended C/C++ General Purpose DSP Libraries I am looking to transition some of my MATLAB algorithms to C/C++ for deployment on target (PowerPC and/or ARM).  Mostly 1D FIR/IIR filter in this instance.

In other domains, there are well-regarded general libraries (both speed and quality) with liberal licencing. For example, Linear Algebra has LAPACK and Eigen (amongst others), and computer vision has OpenCV.

There are well-regarded libraries for specific algorithms, such as FFTW, but what about a collection of general algorithms for 1D signals?

I'm not after DSP-specific libraries, such as for PIC32, CMSIS (ARM Cortex M4), DSPLIB (C64x) or Renesas, but nonetheless has similar functionality.
Maybe a bit late, but since others might land here like me. 

The following are good signal processing libraries/frameworks:
  * https://www.gnuradio.org/ - lots of classic signal processing + cascading options
  * https://root.cern.ch/ - advanced statistical signal processing
Both provide generic facade, fall-back implementations as well as performance optimised sub-libraries (ie. fftw, atlas, LAPACK, gsl, VOLK, ...). 

Together with OpenCV, these probably cover 90++% of use-cases.