configure.ac: Fix typo: 'libmagic-devl' -> 'libmagic-devel'
configure.ac: Don't check for strerror - it's specified by C89, and
we weren't using the result of the check anyway.
configure.ac: Add missing m4 quoting.  Generated configure file is
unchanged.
api/error.cc,backends/chert/chert_btreebase.cc,
backends/chert/chert_table.cc,backends/flint_lock.cc,
backends/glass/glass_table.cc,common/,configure.ac,
net/remoteconnection.cc: Add errno_to_string() function which is
thread-safe where a suitable alternative to strerror() exists.
common/internaltypes.h: Take CHAR_BIT into account when chosing
types for uint2, uint4 and uint8.