Fix crash and memory leak in $aliasctl(COMMAND MATCH)

glob_commands() would run off the end of the irc_command array if given a match that matched
the last command.  It also leaked memory because it used m_s3cat() to construct the string,
then passed that to m_strdup().

This fixes these problems by reworking glob_commands(), and at the same time removes the use
of alloca() and wild_match() by using strncmp() instead to match the start of a string.  Move
glob_commands() to alias.c and make it static since it's only used for aliasctl().

Change the 'name' argument of find_command() and find_dll_command() to const char * at the same
time, so that glob_commands()'s prefix argument can be const char * too.

Changelog

@@ -1,5 +1,7 @@
 [Changes 1.2.2]
 
+* Fix crash and memory leak in $aliasctl(COMMAND MATCH). (caf)
+
 * Fix memory leaks in /CDCC PLIST and /CDCC NOTICE. (caf) 
 
 * Rename reserved identifiers from irc_std.h to fix building on under