added utf8 encoding line to python templates

python breaks if it encounters special characters
in files without specified encoding.
Which is especially funny if you've got umlauts
in your name.
digital: a block should not hold a reference to itself
grcc: set grc file path, which is required for hier blocks
wxgui: fix exception in callback before label set
Merge branch 'maint'
digital: HPD now uses a registered message handler
digital: HPD: fixed tag propagation, minimized calls to work()
digital: fix typo
Merge branch 'maint'
digital: remove stray header file from earlier merge
uninstalled import: Adding overlooked exception handling around imports.
core: making block_registry thread-safe for multiple flowgraphs to access it.
Merge branch 'maint'
runtime: (dup of e0f9a39 for 3.7 structure) making block_registry thread-safe for multiple flowgraphs to access it.
runtime: 2 threading issues with the shared memory system.

1. Making a global mutex for the VM circular buffers to use and lock for multiple top_blocks to handle accessing the memory.

2. Catch the bad_alloc exception once and retry. After 1., this rarely happens unless the thread count gets large (> 20 as an estimate).
grc: fix usage of file descriptor source/sink
analog: fixed agc3_cc_impl GCC assumption
runtime: 2 threading issues with the shared memory system.

1. Making a global mutex for the VM circular buffers to use and lock for multiple top_blocks to handle accessing the memory.

2. Catch the bad_alloc exception once and retry. After 1., this rarely happens unless the thread count gets large (> 20 as an estimate).
Merge branch 'maint'
Merge branch 'master_vmcircbuf_mutex'