Merge branch 'develop' into release/3.5.4

Author: Toni Volkmer

configure.ac

@@ -20,7 +20,7 @@
 
 m4_define([nfft_version_major], [3])
 m4_define([nfft_version_minor], [5])
-m4_define([nfft_version_patch], [3])
+m4_define([nfft_version_patch], [4])
 m4_define([nfft_version_type], [alpha])
 m4_append([NFFT_VERSION], m4_expand([nfft_version_major.nfft_version_minor.nfft_version_patch]))
 m4_append([NFFT_VERSION], m4_expand([nfft_version_type]))