Build with GCC 4.7
Silence autoconf warning

+ autoconf -f -W all
configure.ac:14: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call detected in body
../../lib/autoconf/lang.m4:193: AC_LANG_CONFTEST is expanded from...
../../lib/autoconf/general.m4:2590: _AC_COMPILE_IFELSE is expanded from...
../../lib/autoconf/general.m4:2606: AC_COMPILE_IFELSE is expanded from...
../../lib/m4sugar/m4sh.m4:639: AS_IF is expanded from...
../../lib/autoconf/general.m4:2031: AC_CACHE_VAL is expanded from...
../../lib/autoconf/general.m4:2052: AC_CACHE_CHECK is expanded from...
m4/ax_prog_cxx_cxx0x.m4:26: AX_PROG_CXX_CXX0X is expanded from...
configure.ac:14: the top level
Fix .gitignore for /m4
Use ax_cxx_compile_stdcxx_11.m4 from autoconf-archive
Add check for lambda and range-based for loops in ax_cxx_compile_stdcxx_11.m4
Rename NotMuch namespace to Notmuch
Surround code in notmuch.cc with namespace Notmuch for clarity
Use namespace Notmuch where appropriate
Add more flexible Database class

This allows views to use a shared read-only database connection.
Add ColorID enum entry for None
Make commands a config constant like everything else
Rename ColorID -> Color and Color -> ColorPair
Add convenience ColorMap typedef
Enclose ncurses.cc in namespace NCurses
Move ncurses related initialize/cleanup to ncurses.cc
Use fields instead of functions for configuration
Modify NerConfig instance creation

This allows us to return a const reference in NerConfig::instance() so
we configuration constants can't be modified.
Install terminate handler to handle exceptions instead of using try-catch block
Initialize NCurses colors in NCurses::initialize
Use c++ method for setting default locale