merge: create library of shared code

merge: create library of shared code

 * split out state functions
 * split out parameter functions
 * create library
 * change code to use lib/lib.h
 * move the ascii functions to the library
 * move the base64 functions to the library
 * move the date functions to the library
 * move the exit functions to the library
 * move the md5 functions to the library
 * move the sha1 functions to the library
 * move the memory functions to the library
 * move the message functions to the library
 * move the debug functions to the library
 * move the string functions to the library
 * move the file functions to the library
 * move the buffer functions to the library
 * move the hash functions to the library
 * drop lib.c
 * doxygen: update config
 * rename the library to libmutt