Hide all symbols by default

As mentioned by @abique. Could prevent issues caused by symbol clashes,
and it also greatly reduces the size of all binaries.

CHANGELOG.md

@@ -13,6 +13,8 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 - When `YABRIDGE_DEBUG_LEVEL` is set to 2 or higher and a plugin asks the host
   for the current position in the song, yabridge will now print that position in
   quarter notes and samples as part of the debug output.
+- Symbols in all `libyabridge.so` and all Winelib `.so` files are now hidden by
+  default.
 
 ## [2.1.0] - 2020-11-20
 

meson.build

@@ -26,9 +26,13 @@ individual_host_name_32bit = 'yabridge-host-32'
 group_host_name_64bit = 'yabridge-group'
 group_host_name_32bit = 'yabridge-group-32'
 
-# Disable the use of concepts in Boost.Asio until Boost 1.73 gets released
-# https://github.com/boostorg/asio/issues/312
-compiler_options = ['-DBOOST_ASIO_DISABLE_CONCEPTS']
+compiler_options = [
+  '-fvisibility=hidden',
+  '-fvisibility-inlines-hidden',
+  # Disable the use of concepts in Boost.Asio until Boost 1.73 gets released
+  # https://github.com/boostorg/asio/issues/312
+  '-DBOOST_ASIO_DISABLE_CONCEPTS'
+]
 
 with_bitbridge = get_option('with-bitbridge')
 with_static_boost = get_option('with-static-boost')

src/wine-host/group-host.cpp

@@ -39,7 +39,8 @@
  * The explicit calling convention is needed to work around a bug introduced in
  * Wine 5.7: https://bugs.winehq.org/show_bug.cgi?id=49138
  */
-int __cdecl main(int argc, char* argv[]) {
+int __cdecl __attribute__((visibility("default")))
+main(int argc, char* argv[]) {
     set_realtime_priority();
 
     // Instead of directly hosting a plugin, this process will receive a UNIX

src/wine-host/individual-host.cpp

@@ -32,7 +32,8 @@
  * The explicit calling convention is needed to work around a bug introduced in
  * Wine 5.7: https://bugs.winehq.org/show_bug.cgi?id=49138
  */
-int __cdecl main(int argc, char* argv[]) {
+int __cdecl __attribute__((visibility("default")))
+main(int argc, char* argv[]) {
     set_realtime_priority();
 
     // We pass the name of the VST plugin .dll file to load and the base