Update URL of "Long, Painful History of Time"

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Also rewrapped the paragraph to the same width as the others
Use sb!ext:print-symbol-with-prefix in implicit-generic-function-warning.

 and export this useful function from sb-exr.

 Slight mangling by Paul Khuong.
Make the printing of a slot-unbound error more error tolerant.

Especially against errors coming from custom PRINT-OBJECT methods, in which
case only print the TYPE-OF the instance. Also, print fully qualified
symbol names.

Slightly modified by Paul Khuong.
Provide more info in debugger-disabled-hook.

Before this change if there was an error printing the condition object,
then we didn't even try printing the backtrace afterwards, which can be
a useful source of information even if the condition printing has failed.

Some modifications by Paul Khuong.
Wrap the body of sb-debug:backtrace with with-debug-io-syntax.

 Added with-debug-io-syntax macro.

 Some whitespace changes as well.
In MAKE-THREAD, use WITH-SYSTEM-MUTEX for locking *MAKE-THREAD-LOCK*

Otherwise MAKE-THREAD could be interrupted after having
locked *MAKE-THREAD-LOCK*. If the interrupting code also called
MAKE-THREAD, a recursive lock attempt for *MAKE-THREAD-LOCK* would
occur.

The problem could be easily triggered by

  (MAKE-TIMER ... :THREAD <T or a thread>)

Also move let bindings of SETUP-SEM, REAL-FUNCTION, ARGUMENTS and
INITIAL-FUNCTION and the NOT *GC-INHIBIT* assertion out of the
critical section.

Tests have been added in threads.pure.lisp and timer.impure.lisp.

fixes lp#1180102.
Defer some sanity checks to after testing for value refence to inline functions

 The functional corresponding to an inline function can be marked as dead when
 there remains references in for-value contexts.  Detect such references before
 making sure the function is still live.

 Reported with a reduced test case by Teemu Likonen to sbcl-devel on 2013-06-24.
New contrib: SB-GMP

 This contrib was developed by Stephan Frank to replace some of our
 bignum and rational arithmetic code with calls to libgmp.  Simply
 loading the contrib will transparently accelerate arithmetic on
 large rationals when libgmp is available; if libgmp cannot be found,
 the contrib should change nothing.

 The contrib also wraps additional functions in GNU MP, so that they
 accept and return SBCL-native integers or ratios.  See GNU MP's manual
 for more information.