fwknop: fix compilation with GCC10

Added PKG_LICENSE_FILES.

Added PKG_BUILD_PARALLEL for faster compilation.

Simplified configure arguments.

Small cleanups for consistency between packages.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

net/fwknop/patches/010-gcc10.patch

@@ -0,0 +1,11 @@
+--- a/client/log_msg.h
++++ b/client/log_msg.h
+@@ -29,7 +29,7 @@
+ #ifndef LOG_MSG_H
+ #define LOG_MSG_H
+ 
+-enum
++static enum
+ {
+     LOG_FIRST_VERBOSITY = 0,
+     LOG_VERBOSITY_ERROR = 0,    /*!< Constant to define a ERROR message */