Rely on GModule for adding or not the --export-dynamic linker flag

We explicitly use GModule's .pc since 7b2f0fe, and it provides the
appropriate flag: we don't need to add it ourselves anymore.  Moreover,
since this flag is not needed (nor available) on all platforms (e.g.
Windows or MacOS X), it is safer to let GModule deal with adding it
anyway.

src/Makefile.am

@@ -142,8 +142,6 @@ AM_CFLAGS = -DGEANY_DATADIR=\""$(datadir)"\" \
 			-DGTK \
 			-DG_LOG_DOMAIN=\""Geany"\"
 
-geany_LDFLAGS = -Wl,--export-dynamic
-
 clean-local:
 
 endif

wscript

@@ -362,7 +362,6 @@ def build(bld):
         source          = geany_sources,
         includes        = ['.', 'scintilla/include', 'tagmanager/src'],
         defines         = ['G_LOG_DOMAIN="Geany"', 'GEANY_PRIVATE'],
-        linkflags       = [] if is_win32 else ['-Wl,--export-dynamic'],
         uselib          = ['GTK', 'GLIB', 'GMODULE', 'GIO', 'GTHREAD', 'WIN32', 'SUNOS_SOCKET'],
         use             = ['scintilla', 'ctags', 'tagmanager', 'mio'])