RCORE: fix Unicode::isvalid() for Unicode noncharacters

See Unicode Corrigendum #9: Clarification About Noncharacters:
	http://www.unicode.org/versions/corrigendum9.html
RCORE: prevent excessive mutex locking for empty string blob accesses
RCORE: provide Test::normal() to complement slow() and logging()
BUILD: include basic blob loading test into installcheck target
BUILD: workaround for g++<=4.7 missing --enable-libstdcxx-time
TESTS: signedness fixup
AIDA: fix NULL use in integer context
RCORE: make use of the strerror_r() return string
TESTS: create temporary filename from tid() and rand() to avoid using deprecated tmpnam(3)
Merge branch 'build-fixups'

* build-fixups:
  TESTS: create temporary filename from tid() and rand() to avoid using deprecated tmpnam(3)
  RCORE: make use of the strerror_r() return string
  AIDA: fix NULL use in integer context
  TESTS: signedness fixup
  BUILD: workaround for g++<=4.7 missing --enable-libstdcxx-time
  BUILD: include basic blob loading test into installcheck target
  RCORE: provide Test::normal() to complement slow() and logging()
  RCORE: prevent excessive mutex locking for empty string blob accesses
  RCORE: fix Unicode::isvalid() for Unicode noncharacters
UI: sinfex.cc: work around bison & flex disagreeing on nullptr vs 0 for YY_NULL