fixes #143 Protocols and transports should be "configurable"

This makes all the protocols and transports optional.  All
of them except ZeroTier are enabled by default, but you can
now disable them (remove from the build) with cmake options.

The test suite is modified so that tests still run as much
as they can, but skip over things caused by missing functionality
from the library (due to configuration).

Further, the constant definitions and prototypes for functions
that are specific to transports or protocols are moved into
appropriate headers, which should be included directly by
applications wishing to use these.

We have also added and improved documentation -- all of the
transports are documented, and several more man pages for
protocols have been added.  (Req/Rep and Surveyor are still
missing.)

1 files changed, 11 insertions, 6 deletions

diff --git a/docs/nng_inproc.adoc b/docs/nng_inproc.adoc
index 9e044f6d..a6d83c95 100644
--- a/docs/nng_inproc.adoc
+++ b/docs/nng_inproc.adoc
@@ -47,8 +47,7 @@ URI Format
 
 This transport uses URIs using the scheme `inproc://`, followed by
 an arbitrary string of text, terminated by a `NUL` byte.  The
-entire URI must be less than `NNG_MAXADDRLEN` bytes long, including
-the terminating `NUL`.
+entire URI must be less than `NNG_MAXADDRLEN` bytes long.
 
 Multiple URIs can be used within the
 same application, and they will not interfere with one another.
@@ -65,16 +64,22 @@ When using an `nng_sockaddr` structure, the actual structure is of type
 
 [source,c]
 --------
-#define NNG_AF_INPROC 1
+#define NNG_AF_INPROC 1 <1>
 #define NNG_MAXADDRLEN 128
 
-struct nng_sockaddr_inproc {
+typedef nng_sockaddr_inproc {
+    // <2>
     uint16_t sa_family;                  // must be NNG_AF_INPROC
-    uint32_t sa_path[NNG_MAXADDRLEN];    // arbitrary "path"
+    char     sa_path[NNG_MAXADDRLEN];    // arbitrary "path"
+    //
 }
 --------
+<1> The values of these macros may change, so applications
+should avoid depending upon their values and instead use them symbolically.
+<2> Other members may be present, but only those listed here
+are suitable for application use.
 
-The `sa_family` member will have the value `NNG_AF_INPROC` (1).
+The `sa_family` member will have the value `NNG_AF_INPROC`.
 The `sa_path` member is an ASCIIZ string, and may contain any characters,
 terminated by a `NUL` byte.