Hide every symbol except ZNCModInfo from modules.

This means that now it's possible to have the same class names in
different modules, which reduces chances of weird errors.

Thanks to mclc for noticing this.

Modules.h

@@ -53,9 +53,15 @@ template<class M> CGlobalModule* TModLoadGlobal(ModHandle p,
 	return new M(p, sModName, sModPath);
 }
 
+#if HAVE_VISIBILITY
+# define MODULE_EXPORT __attribute__((__visibility__("default")))
+#else
+# define MODULE_EXPORT
+#endif
+
 #define MODCOMMONDEFS(CLASS, DESCRIPTION, GLOBAL, LOADER) \
 	extern "C" { \
-		bool ZNCModInfo(double dCoreVersion, CModInfo& Info); \
+		MODULE_EXPORT bool ZNCModInfo(double dCoreVersion, CModInfo& Info); \
 		bool ZNCModInfo(double dCoreVersion, CModInfo& Info) { \
 			if (dCoreVersion != VERSION) \
 				return false; \

configure.ac

@@ -28,6 +28,7 @@ AC_PROG_GREP
 AC_PROG_SED
 AC_CANONICAL_HOST
 AC_SYS_LARGEFILE
+gl_VISIBILITY
 
 appendLib () {
 	if test "$LIBS" != ""; then
@@ -268,6 +269,7 @@ AC_ARG_WITH( [module-data-prefix],
 	[DATADIR="${datadir}/znc"] )
 
 appendMod "$CXXFLAGS"
+appendMod "$CFLAG_VISIBILITY"
 
 if test -z "$ISSUN" -a -z "$ISDARWIN" -a -z "$ISCYGWIN"; then
 	# This is an unknown compiler flag on some OS

modules/modperl/module.h

@@ -10,6 +10,9 @@
 
 #include "Modules.h"
 
+#if HAVE_VISIBILITY
+#pragma GCC visibility push(default)
+#endif
 class CPerlModule : public CModule {
 	CString m_sPerlID;
 	VWebSubPages* _GetSubPages();
@@ -171,3 +174,6 @@ inline double GetVersion() {
 inline CString GetVersionExtra() {
 	return VERSION_EXTRA;
 }
+#if HAVE_VISIBILITY
+#pragma GCC visibility pop
+#endif

modules/modpython/module.h

@@ -15,6 +15,9 @@ public:
 
 class CModPython;
 
+#if HAVE_VISIBILITY
+#pragma GCC visibility push(default)
+#endif
 class CPyModule : public CModule {
 	PyObject* m_pyObj;
 	CModPython* m_pModPython;
@@ -224,3 +227,6 @@ public:
 	}
 };
 
+#if HAVE_VISIBILITY
+#pragma GCC visibility pop
+#endif