Fix small one-time leaks in start.c initlibltdl()

Library routine lt_dladdsearchdir() takes a string argument, but always
copies it before use.  It did not need to be strdup()ed.  This was *very*
defensive coding... ;)

gutils/fsys.c :: getFontForgeUserDir() always newly allocates the returned
string value.  This must be freed when no longer needed.  Adrien has fixed a
couple of the several uses of this routine.  All the rest need to be fixed.

The former routine getPfaEditDir() would generate the requested string once,
the first time, and retain that for further usages.  E.g.
      char *getPfaEditDir(char *buffer) {
          static char *editdir = NULL;
          :   :    :   :    :   :    :   :    :   :
          editdir = copy(buffer);
          return( editdir );
Thus strings would leak at most once, and even code like the two consecutive
calls below would still only leak once.  Now that we allocate new strings
each time, we need to free() after each use.
Fix small leaks in groups.c getPfaEditGroups()

Another use of the recent routine gutils/fsys.c :: getFontForgeUserDir()
that requires a free() of the newly allocated string after use.
Fix small leak in namelist.c LoadNamelistDir()

Another use of the recent routine gutils/fsys.c :: getFontForgeUserDir()
that requires a free() of the newly allocated string after use.
Fix small leak in startui.c ensureDotFontForgeIsSetup()

Another use of the recent routine gutils/fsys.c :: getFontForgeUserDir()
that requires a free() of the newly allocated string after use.

Tested and leak now gone from valgrind reports.
Fix small leak in autosave.c getAutoDirName()

Another use of the recent routine gutils/fsys.c :: getFontForgeUserDir()
that requires a free() of the newly allocated string after use.

Tested and leak has disappeared from valgrind reports.
Fix leak of strings in openfontdlg.c FVOpenFont()

A list of glyph list names was created for display in the "Open Font"
dialog.  The name strings were stuffed into the dialog creation data
structures.  After the dialog was dismissed, nobody was free()ing those
name strings.

Moved the names list array free() to end of dialog routine, and first
used that list to locate and free() all the name strings.
Revert dfa3d83a (fix for strtod with wrong locale in issue #630)
Use c-strtod module from gnulib for a better fix for issue #630
Merge pull request #1601 from tshinnic/leak_fvopenfont_nlnames_openfontdlgc

Fix leak of strings in openfontdlg.c FVOpenFont()
Merge pull request #1600 from tshinnic/leak_getuserdir_autosavec

Fix small leak in autosave.c getAutoDirName()
Merge pull request #1599 from tshinnic/leak_getuserdir_startuic_1

Fix small leak in startui.c ensureDotFontForgeIsSetup()
Merge pull request #1597 from tshinnic/leak_getuserdir_namelistc

Fix small leak in namelist.c :: LoadNamelistDir()
Merge pull request #1593 from tshinnic/leak_getuserdir_groupsc

Fix small leaks in groups.c :: getPfaEditGroups()
Merge pull request #1592 from tshinnic/leak_getuserdir_ltdl_startc

Fix small one-time leaks in start.c :: initlibltdl()
Merge pull request #1604 from rrthomas/master

Fix #630 more neatly, using gnulib's c-strtod
Fix some errors found by tcc

Also remove an unused function.
Reinstate unused function SplitMonotonicAt
Merge pull request #1605 from rrthomas/master

Fix some errors found by tcc