Merge bug fixes from Trunk:

Mostly correct typos as per https://svn.boost.org/trac/boost/ticket/7806
Also fix cpp_dec_float docs and add some static asserts to catch misuse.
Fix performance bottleneck in cpp_int's gcd implementation.

[SVN r82122]

doc/pdf/build

@@ -8,7 +8,7 @@ echo Boost version tag = $boost_version
 (cd ../../libs/geometry/doc/src/docutils/tools/doxygen_xml2qbk && bjam release) 2>&1 | tee -a build.log
 (cd ../../libs/functional/overloaded_function/doc && rm -rf *.pdf && bjam -a pdfinstall && cp *.pdf ../../../../doc/pdf) 2>&1 | tee -a build.log
 (cd ../../libs/local_function/doc && rm -rf *.pdf && bjam -a pdfinstall && cp *.pdf ../../../doc/pdf) 2>&1 | tee -a build.log
-(cd ../../libs/utility/identity_type/doc && rm -rf *.pdf && bjam -a pdfinstall && cp *.pdf ../../../../doc/pdf) 2>&1 | tee -a build.log
+(cd ../../libs/utility/identity_type/doc && rm -rf *.pdf && bjam -a pdf_doc_install && cp *.pdf ../../../../doc/pdf) 2>&1 | tee -a build.log
 cp ../../dist/bin/doxygen_xml2qbk* /usr/local/bin
 (cd ../../libs/geometry/doc && rm -rf *.pdf && ./make_qbk.py && bjam pdfinstall -a xsl:param=fop1.extensions=1 xsl:param=xep.extensions=0 && cp *.pdf ../../../doc/pdf) 2>&1 | tee -a build.log
 bjam -a --enable-index pdf -d2 xsl:param=fop1.extensions=0 xsl:param=xep.extensions=1 2>&1 | tee -a build.log
@@ -18,3 +18,4 @@ mv *.pdf boost_${boost_version}_pdf
 
 
 
+

libs/multiprecision

@@ -1 +1 @@
-Subproject commit a4c6303ad8555badd2bc3d946fc159bab54703b6
+Subproject commit 5260e3fdb270d50f65ca0125cf64d260b13e0d2f