modtool: removing RTLD_GLOBAL hack for swig in gr-modtool.

This was removed from GNU Radio a while ago due to newer issues. Looks like it's affecting OOT modules as well.
volk: add check for posix_memalign for OSs that do not directly set _XOPEN_SOURCE or _POSIX_C_SOURCE; define and use the new variable when found.
modtool: Fixed a bug in makexml for int-type io signatures
logger: adding new configure_default_logger function to make it easier to get log file info on logger setup.
cmake: adding a function to allow components to reference submodules for display.

Mostly designed for gr-audio to print out which audio machines are enabled in the build.
audio: modified the audio registration system.

Instead of static functions and macros, this just uses simple ifdefs in the code to register new audio components if cmake found them. The code is more complicated for the developer, if we ever add a new audio machine. But this allows us to use gr-audio in statically linked cases.
volk: simplifies and fixes thread safety issue in volk_malloc/free.
Merge branch 'maint'
Merge remote-tracking branch 'arya/audio_registration'
logger: poor placement of the function inside the ifdefs. Moving outside to make the function accessible with any logger setting.
blocks: delay block cannot be initialized with a negative number.

This commit puts in a check in the constructor and better
documentation about the behavior.
Merge branch 'maint'
grc: switch execute action icon to media_play
volk: adds a volk_malloc/free case for Windows to use its _aligned_malloc.
grc: renaming 'Build' menu to 'Run'

Suggested by Mike Ossmann
cmake: make sure our local CMake Modules path comes first.
cmake: fix FindUHD.cmake to first check to see if UHD installed its own version of FindUHD, and if so use it; if not, revert to current behavior.
Merge remote-tracking branch 'martin/modtool/bugfix' into maint
Fix for #647 - GUI Tabs do not switch on WX GUI Scope sink channels on OSX

With this patch, the bug is not showing anymore. It was only tested by
me on Mac OS X - not on Linux nor other platforms.
The possible regressions introduced by fix should be limited to the
notebook chooser forms only.
Merge remote-tracking branch 'skoslowski/grc_exec_icon'