Details:
- Added a new option to 'configure' that allows the user to specify a
  list of symbols to omit from the library. The format of the option is
  --omit-symbols=LIST where LIST is a comma-separated list of symbol
  names (excluding any trailing underscore). This list is parsed into
  a list of #define directives that causes the relevant parts of BLIS
  to be ignored (or not). As such, the nature of this option is to only
  support omitting symbols which have been pre-identified as potential
  troublemakers when linking BLIS with other libraries such as LAPACK
  or ScaLAPACK. (This list may grow in the future as additional symbols
  are identified.)
- Re-implemented the --enable-scalapack-compat configure option to
  utilize the underlying --omit-symbols=LIST infrastructure.
- Implemented an --enable-lapack-compat option, which omits all of the
  known problematic symbols currently supported for omission.
- This commit addresses Issue #816. Thanks to Timo Betcke for bringing
  it to our attention and to Devin Matthews for his advice and for
  his initial implementation of --enable-scalapack-compat (PR #813).
- CREDITS file update.

Details:
- Leave lsame_() and xerbla_() prototypes enabled even when their
  respective symbols are omitted from the library.
- Fixed copy-and-paste bug.
- Fixed typos in the #define directives.