subprojects: add libpcap with plugin loader support

Add libpcap as a meson wrap subproject with three patches on top of
upstream commit bac2884b. These patches implement the plugin loader
proposed in the-tcpdump-group/libpcap#1659:

 - runtime plugin loader for external capture modules
 - timestamp type accessors for adapter code
 - complete accessor API for tcpdump feature parity

The meson.build exposes a plugindir variable via declare_dependency()
so consumers can install plugins in the right location.

Signed-off-by: Robin Jarry <rjarry@redhat.com>

Author: rjarry

.gitignore

@@ -21,4 +21,5 @@
 /subprojects/dpdk-*
 /subprojects/libecoli-*
 /subprojects/frr-*
+/subprojects/libpcap
 /subprojects/packagecache

subprojects/libpcap.wrap

@@ -0,0 +1,12 @@
+[wrap-git]
+url = https://github.com/the-tcpdump-group/libpcap
+revision = bac2884bfabe20f9ff0f711eb9eb7589569e6a01
+depth = 1
+patch_directory = libpcap
+diff_files =
+	libpcap/0001-plugin-add-runtime-plugin-loader-for-external-captur.patch,
+	libpcap/0002-plugin-expose-timestamp-type-accessors-for-adapter-c.patch,
+	libpcap/0003-plugin-complete-accessor-API-for-tcpdump-feature-par.patch
+
+[provide]
+dependency_names = libpcap