Remove custom main() from test_PipeCapture (!22)

After removing Glib::thread_init() from test_PipeCapture's main() all it
does is exactly what the built in Google Test main() does [1][2].  So
use that instead like the other unit test programs do.

[1] Google Test, Primer, Writing the main() Function
    https://github.com/google/googletest/blob/master/googletest/docs/primer.md#writing-the-main-function

[2] Google Test 1.8.0, gtest_main.cc::main()
    file: lib/gtest/src/gtest_main.cc
    https://github.com/google/googletest/blob/release-1.8.0/googletest/src/gtest_main.cc#L34

Closes !22 - Increase minimums to libparted 2.2 and glibmm 2.32

tests/Makefile.am

@@ -34,5 +34,4 @@ test_PasswordRAMStore_LDADD   =  \
 test_PipeCapture_SOURCES  = test_PipeCapture.cc
 test_PipeCapture_LDADD    =  \
 	$(top_builddir)/src/PipeCapture.$(OBJEXT)  \
-	$(GTEST_LIBS)                              \
+	$(LDADD)
-	$(top_builddir)/lib/gtest/lib/libgtest.la

tests/test_PipeCapture.cc

@@ -411,15 +411,3 @@ TEST_F( PipeCaptureTest, LineDisciplineSkipCtrlAB )
 }
 
 }  // namespace GParted
-
-// Custom Google Test main().
-// Reference:
-// *   Google Test, Primer, Writing the main() Function
-//     https://github.com/google/googletest/blob/master/googletest/docs/primer.md#writing-the-main-function
-int main( int argc, char **argv )
-{
-	printf("Running main() from %s\n", __FILE__ );
-	testing::InitGoogleTest( &argc, argv );
-
-	return RUN_ALL_TESTS();
-}