Remove src/platform

All the files in src/platform are currently unused and unnecessary. See below:

* `mingw/alloca.h`: unused throughout project
* `msc/sys/param.h`:
    1. In `fix_darwin.patch`, `sys/param.h` is well-defined to be used only in OpenBSD environment
    2. `int-util.h` already handles when `sys/param.h` is not present and injects its own values
    3. `db_drivers/liblmdb/mdb.c` is a similar situation: already explicity handles different platforms
    4. `src/crypto/chacha.h` uses `int-util.h` for endianness context
* `msc/alloca.h`: unused
* `msc/inline_c.h`: not needed. the `inline` keyword is supported for C99 I believe, and certainly for C11, C14+
* `msc/stdbool.h`: `stdbool.h` is standard since C99, and MSVC has supported it for a long time (~10 years)

CMakeLists.txt

@@ -701,7 +701,7 @@ endif()
 include(CheckTrezor)
 
 if(MSVC)
-  add_definitions("/bigobj /MP /W3 /GS- /D_CRT_SECURE_NO_WARNINGS /wd4996 /wd4345 /D_WIN32_WINNT=0x0600 /DWIN32_LEAN_AND_MEAN /DGTEST_HAS_TR1_TUPLE=0 /FIinline_c.h /D__SSE4_1__")
+  add_definitions("/bigobj /MP /W3 /GS- /D_CRT_SECURE_NO_WARNINGS /wd4996 /wd4345 /D_WIN32_WINNT=0x0600 /DWIN32_LEAN_AND_MEAN /DGTEST_HAS_TR1_TUPLE=0 /D__SSE4_1__")
   # set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /Dinline=__inline")
   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} /STACK:10485760")
   if(STATIC)
@@ -709,7 +709,6 @@ if(MSVC)
       string(REPLACE "/MD" "/MT" ${VAR} "${${VAR}}")
     endforeach()
   endif()
-  include_directories(SYSTEM src/platform/msc)
 else()
   include(TestCXXAcceptsFlag)
   message(STATUS "Building on ${CMAKE_SYSTEM_PROCESSOR} for ${ARCH}")
@@ -786,7 +785,6 @@ else()
     set(WARNINGS "${WARNINGS} -Wno-error=unused-value -Wno-error=unused-but-set-variable")
     set(MINGW_FLAG "${MINGW_FLAG} -DWIN32_LEAN_AND_MEAN")
     set(Boost_THREADAPI win32)
-    include_directories(SYSTEM src/platform/mingw)
     # mingw doesn't support LTO (multiple definition errors at link time)
     set(USE_LTO_DEFAULT false)
     set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,--stack,10485760")