Fixed link error when building only shared library.

Details:
- Fixed a linker error that occurred when attempting to compile and link
  the testsuite and/or BLAS test drivers after having configured BLIS to
  only generate a shared library (no static library). The chosen
  solution involved
  (1) adding the local library path, $(BASE_LIB_PATH), to the search
      paths for the shared library via the link option
      -Wl,-rpath,$(BASE_LIB_PATH).
  (2) adding a local symlink to $(BASE_LIB_PATH) that uses the .so major
      version number so that ld would find the shared library at
      execution time.
  Thanks to Sajid Ali for reporting this issue, to Devin Matthews for
  pointing out the need for the -rpath option, and to Devangi Parikh for
  helping Sajid isolate the problem.
- Added #include <ctype.h> to bli_system.h to avoid a compiler warning
  resulting from using toupper() from bli_string.c without a prototype.
  Thanks again to Sajid Ali, whose build log revealed this compiler
  warning.
- Added '*.so.*' to .gitignore.
- CREDITS file update.

frame/include/bli_system.h

@@ -42,6 +42,7 @@
 #include <stdarg.h>
 #include <float.h>
 #include <errno.h>
+#include <ctype.h>
 
 // Determine if we are on a 64-bit or 32-bit architecture.
 #if defined(_M_X64) || defined(__x86_64) || defined(__aarch64__) || \