Added more documentation

INSTALL.md

@@ -5,13 +5,15 @@
 - Xlib
 - Xt
 - Motif
+- MWM
 - A C compiler
 - brightnessctl (for xmbrightness)
+- xwallpaper
 
 Installing via APK:
 
 ```
-# apk add libx11 libx11-dev libxt libxt-dev motif motif-dev clang
+# apk add libx11 libx11-dev libxt libxt-dev motif motif-dev mwm xwallpaper clang
 ```
 
 ## libXmd
@@ -33,3 +35,20 @@ subdirectories:
 # cd <application>
 # ./build.sh install
 ```
+
+## Replicants
+
+Xmd provides something called replicants, which are dynamically loaded widgets
+that can be placed inside of xmpanel. They can be installed using `./build.sh`
+in their respective subdirectories:
+
+```
+# cd replicants/<replicant>
+# ./build.sh install
+```
+
+## Session
+
+Xmd includes a startup script and assorted "glue code" to facilitate using it as
+a desktop environment. It can be installed using `./install.sh` in the `session`
+directory.

README.md

@@ -1,3 +1,3 @@
 # Xmd
 
-A collection of X11 Motif desktop utilities written in C99.
+An X11/Motif desktop environment written in C99.

libXmd/README.md

@@ -0,0 +1,5 @@
+# libXmd
+
+This library contains code that is common to Xmd applications. The interface to
+its functionality is divided among several header files which also contain
+documentation comments.

libXmd/include/Xmd/Exec.h

@@ -5,8 +5,18 @@
 #include <stdio.h>
 #include <sys/types.h>
 
+/* XmdVaPipedExecPath is like XmdPipedExecPath, but it takes in a vararg list to
+   use as the "args" array. The vararg list must be terminated by NULL. */
 FILE *XmdVaPipedExecPath (const String file, pid_t *child, String mode, ...);
 
+/* XmdPipedExecPath is like popen(), but takes in an explicit command name and
+   argument list instead of a shell command. The argument list must be
+   terminated by NULL. "file" is searched for in PATH, and it is executed as a
+   child process with the specified args. The PID of the child is stored at the
+   location of "child".
+   
+   To correctly close the connection to the child process, first fclose() the
+   returned file, and then call waitpid() on the child PID. */
 FILE *XmdPipedExecPath (const String file, pid_t *child, String mode, String const argv[]);
 
 #endif