Added support for C99 complex types/arithmetic.

Details:
- Added support for C99 complex types to bli_type_defs.h and overloaded
  complex arithmetic to the scalar-level macros in include/level0. This
  includes a somewhat substantial reorganization and re-layering of much
  of the existing machinery present in the level0 macros.
- Added new #define for BLIS_ENABLE_C99_COMPLEX to bli_config.h files,
  commented-out by default, which optionally enables the use of built-in
  C99 complex types and arithmetic.
- Minor changes to clarksville and reference configs' make_defs.mk files.
- Removed macro definitions from bli_param_macro_defs.h which was not being
  used (bli_proj_dt_to_real_if_imag_eq0).

config/reference/bli_config.h

@@ -45,6 +45,11 @@
 #define BLIS_NUM_FP_TYPES                4
 #define BLIS_MAX_TYPE_SIZE               sizeof(dcomplex)
 
+// Enable use of built-in C99 "float complex" and "double complex" types and
+// associated overloaded operations and functions? Disabling results in
+// scomplex and dcomplex being defined in terms of simple structs.
+//#define BLIS_ENABLE_C99_COMPLEX
+
 
 
 // -- MULTITHREADING -----------------------------------------------------------
@@ -131,6 +136,7 @@
 #define BLIS_ENABLE_BLAS2BLIS_INT64
 
 // Fortran-77 name-mangling macros.
+#define PASTEF770(name)                        name ## _
 #define PASTEF77(ch1,name)       ch1        ## name ## _
 #define PASTEF772(ch1,ch2,name)  ch1 ## ch2 ## name ## _