Remove Boost.StaticAssert submodule

[Lastique]

Since Boost.StaticAssert has been merged into Boost.Config, this submodule can be removed once all Boost libraries have removed references to it. For tracking purposes, here is the list of the relevant PRs:

• Remove dependencies on Boost.StaticAssert accumulators#67

• Remove dependencies on Boost.StaticAssert algorithm#130

• Remove dependencies on Boost.StaticAssert align#24

• Remove dependencies on Boost.StaticAssert assert#44

• Remove dependencies on Boost.StaticAssert assign#50

• Remove dependencies on Boost.StaticAssert array#30

• Remove dependencies on Boost.StaticAssert beast#3074

• Remove dependencies on Boost.StaticAssert bimap#51

• Remove dependencies on Boost.StaticAssert charconv#287

• Remove dependencies on Boost.StaticAssert chrono#81

• Remove dependencies on Boost.StaticAssert circular_buffer#54

• Remove dependencies on Boost.StaticAssert cobalt#262

• Remove dependencies on Boost.StaticAssert compute#898

• Remove dependencies on Boost.StaticAssert concept_check#47

• Remove dependencies on Boost.StaticAssert config#533

• Remove dependencies on Boost.StaticAssert contract#41

• Remove dependencies on Boost.StaticAssert date_time#250

• Remove dependencies on Boost.StaticAssert endian#60

• Remove dependencies on Boost.StaticAssert function#57

• Remove dependencies on Boost.StaticAssert function_types#19

• Remove dependencies on Boost.StaticAssert fusion#279

• Remove dependencies on Boost.StaticAssert geometry#1447

• Remove dependencies on Boost.StaticAssert gil#786

• Remove dependencies on Boost.StaticAssert graph#450

• Remove dependencies on Boost.StaticAssert graph_parallel#45

• Remove dependencies on Boost.StaticAssert hash2#46

• Remove dependencies on Boost.StaticAssert heap#57

• Remove dependencies on Boost.StaticAssert histogram#419

• Remove dependencies on Boost.StaticAssert icl#52

• Remove dependencies on Boost.StaticAssert interval#48

• Remove dependencies on Boost.StaticAssert io#17

• Remove dependencies on Boost.StaticAssert iostreams#190

• Remove dependencies on Boost.StaticAssert lexical_cast#95

• Remove dependencies on Boost.StaticAssert lockfree#126

• Remove dependencies on Boost.StaticAssert math#1351

• Remove dependencies on Boost.StaticAssert metaparse#22

• Remove dependencies on Boost.StaticAssert move#63

• Remove dependencies on Boost.StaticAssert mp11#112

• Remove dependencies on Boost.StaticAssert mpi#177

• Remove dependencies on Boost.StaticAssert mpl#91

• Remove dependencies on Boost.StaticAssert mqtt5#46

• Remove dependencies on Boost.StaticAssert multi_array#42

• Remove dependencies on Boost.StaticAssert multi_index#91

• Remove dependencies on Boost.StaticAssert mysql#497

• Remove dependencies on Boost.StaticAssert odeint#105

• Remove dependencies on Boost.StaticAssert pfr#229

• Remove dependencies on Boost.StaticAssert phoenix#125

• Remove dependencies on Boost.StaticAssert program_options#155

• Remove dependencies on Boost.StaticAssert property_map#36

• Remove dependencies on Boost.StaticAssert property_map_parallel#4

• Remove dependencies on Boost.StaticAssert property_tree#134

• Remove dependencies on Boost.StaticAssert proto#39

• Remove dependencies on Boost.StaticAssert ptr_container#44

• Remove dependencies on Boost.StaticAssert python#509

• Remove dependencies on Boost.StaticAssert random#152

• Remove dependencies on Boost.StaticAssert range#162

• Remove dependencies on Boost.StaticAssert rational#57

• Remove dependencies on Boost.StaticAssert redis#386

• Remove dependencies on Boost.StaticAssert regex#269

• Remove dependencies on Boost.StaticAssert serialization#340

• Remove dependencies on Boost.StaticAssert signals2#84

• Remove dependencies on Boost.StaticAssert smart_ptr#122

• Remove dependencies on Boost.StaticAssert sort#109

• Remove dependencies on Boost.StaticAssert spirit#846

• Remove dependencies on Boost.StaticAssert stacktrace#223

• Remove dependencies on Boost.StaticAssert statechart#27

• Remove dependencies on Boost.StaticAssert system#139

• Remove dependencies on Boost.StaticAssert test#474

• Remove dependencies on Boost.StaticAssert thread#417

• Remove dependencies on Boost.StaticAssert tuple#32

• Remove dependencies on Boost.StaticAssert type_traits#203

• Remove dependencies on Boost.StaticAssert typeof#27

• Remove dependencies on Boost.StaticAssert ublas#198

• Remove dependencies on Boost.StaticAssert units#66

• Remove dependencies on Boost.StaticAssert unordered#341

• Remove dependencies on Boost.StaticAssert uuid#192

• Remove dependencies on Boost.StaticAssert variant#115

• Remove dependencies on Boost.StaticAssert wave#245

• Remove dependencies on Boost.StaticAssert xpressive#29

• Remove testing of Boost.StaticAssert boostdep#33

• Remove dependencies on Boost.StaticAssert cmake#103

• Remove dependencies on Boost.StaticAssert boost-ci#313

Once these PRs are merged and propagate to master, I propose to add a release note for the next Boost release to notify users that the submodule is deprecated and will soon be removed. Then, after 3 Boost releases, actually remove the submodule.

CC @pdimov