Move list of ignored file to tests/ directory

Makes the tests/ directory more self-contained and the top-level
.gitgnore shorter.

.gitignore

@@ -69,21 +69,3 @@ scripts/build-w32.sh.*
 scripts/build-w64.sh.*
 src/hamlibdatetime.h
 src/libhamlib.def
-tests/ampctl
-tests/ampctld
-tests/rigctl
-tests/rigctlcom
-tests/rigctld
-tests/rigctlsync
-tests/rigctltcp
-tests/rigfreqwalk
-tests/rigmem
-tests/rigsmtr
-tests/rigswr
-tests/rigtestlibusb
-tests/rigtestmcast
-tests/rigtestmcastrx
-tests/rotctl
-tests/rotctld
-tests/testlibusb
-tuner_control.log

tests/.gitignore

@@ -0,0 +1,18 @@
+ampctl
+ampctld
+rigctl
+rigctlcom
+rigctld
+rigctlsync
+rigctltcp
+rigfreqwalk
+rigmem
+rigsmtr
+rigswr
+rigtestlibusb
+rigtestmcast
+rigtestmcastrx
+rotctl
+rotctld
+testlibusb
+tuner_control.log