Define _POSIX_C_SOURCE in bli_system.h.

Details:
- Added
    #ifndef _POSIX_C_SOURCE
    #define _POSIX_C_SOURCE 200809L
    #endif
  to bli_system.h so that an application that uses BLIS (specifically,
  an application that #includes blis.h) does not need to remember to
  #define the macro itself (either on the command line or in the code
  that includes blis.h) in order to activate things like the pthreads.
  Thanks to Christos Psarras for reporting this issue and suggesting
  this fix.
- Commented out #include <sys/time.h> in bli_system.h, since I don't
  think this header is used/needed anymore.
- Comment update to function macro for bli_?normiv_unb_var1() in
  frame/util/bli_util_unb_var1.c.

frame/include/bli_system.h

@@ -36,6 +36,12 @@
 #ifndef BLIS_SYSTEM_H
 #define BLIS_SYSTEM_H
 
+// NOTE: If not yet defined, we define _POSIX_C_SOURCE to make sure that
+// various parts of POSIX are defined and made available.
+#ifndef _POSIX_C_SOURCE
+#define _POSIX_C_SOURCE 200809L
+#endif
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
@@ -111,7 +117,8 @@
 #elif BLIS_OS_OSX
   #include <mach/mach_time.h>
 #else
-  #include <sys/time.h>
+  //#include <sys/time.h>
+
   #include <time.h>
 #endif
 

frame/util/bli_util_unb_var1.c

@@ -466,7 +466,7 @@ void PASTEMAC(ch,varname) \
 		/* If the absolute value of the current element exceeds that of
 		   the previous largest, save it and its index. If NaN is
 		   encountered, then treat it the same as if it were a valid
-		   value that was smaller than any previously seen. This
+		   value that was larger than any previously seen. This
 		   behavior mimics that of LAPACK's ?lange(). */ \
 		if ( abs_chi1_max < abs_chi1 || bli_isnan( abs_chi1 ) ) \
 		{ \