Partially revert "matioConfig.h.in has to be updated regarding the recent changes in the configure"

This partially reverts commit 96a553632d921cbd55c68e71277d17cc39ce1203.
Fix calls to malloc with allocation size of 0 bytes

* src/mat.c (Mat_VarCreate): Check that matvar->nbytes is greater than
      0 before calling malloc

* src/mat73.c (Mat_H5ReadGroupInfo): If numel or nfields is less than 1
      return before allocating fields

* src/matvar_struct.c (Mat_VarCreateStruct): Check that matvar is not NULL
      and nmemb and nfields is greater than 0 before calling malloc
Fix return variable type

* src/mat73.c (Mat_TypeToClass73): Assign and return class_type
Remove a number of unused variables

* src/mat5.c (WriteCompressedCharData,WriteCompressedCellArrayField,
  WriteCompressedStructField,ReadData5): Remove unused variable

* src/mat73.c: Remove dims1

* src/mat73.c (Mat_H5ReadGroupInfo,Mat_H5ReadNextReferenceInfo,
  Mat_H5ReadNextReferenceData,Mat_VarWriteSparse73,Mat_VarRead73,
  Mat_VarReadNextInfo73): Remove unused variables

* src/read_data.c (ReadCompressedDataSlab1): Remove unused variables
Move pre-preprocessor version to public config and add new version format

* configure.ac: Added substitute of new pre-processor token MATIO_VERSION
      that makes testing the entire version number easier

* src/matio_pubconf.h.in (MATIO_VERSION): Added

* src/matioConfig.h.in (MATIO_MAJOR_VERSION,MATIO_MINOR_VERSION,
  MATIO_RELEASE_LEVEL): Moved to src/matio_pubconf.h.in
Add function to get the filename from MAT file structure

* src/matio.h,src/mat.c (Mat_GetFilename): Added

* documentation/Mat_GetFilename.3: Added

* documentation/Makefile.am (dist_man3_MANS): Added Mat_GetFilename.3
Add function to get the file version from MAT file structure

* src/matio.h,src/mat.c (Mat_GetVersion): Added

* documentation/Mat_GetVersion.3: Added

* documentation/Mat_GetFilename.3: Added reference to Mat_GetVersion

* documentation/Makefile.am (dist_man3_MANS): Added Mat_GetVersion.3
Fix bugs reading structures using linear indexing

* src/matvar_struct.c (Mat_VarGetStructsLinear): Set the dimensions of
      the returned struture to be a column vector with edge elements

* src/matvar_struct.c (Mat_VarGetStructsLinear): Account for number of
      fields in the stride of the output and input data pointers
Add test for linear indexing of structures

* test/struct_api.at: Added test

* test/test_mat.c (test_struct_api_getlinear): Added

* test/test_mat.c (main): Check for test name "struct_api_getlinear"
Use internal number of fields to free structure arrays

* src/mat.c (Mat_VarFree): Use matvar->internal->num_fields as the number
      of fields
Use number of elements to free cell arrays

* src/mat.c (Mat_VarFree): Use nmemb as the number of elements instead of
      dividing nbytes by data_size
Do not free structure fields/cell elements if memory conserve set

* src/mat.c (Mat_VarFree): Do not free structure fields of cell array
      elements of the struct/cell was set to conserve memory
Fix bugs reading structures using slices in each dimension

* src/matvar_struct.c (Mat_VarGetStructs): Fix the indexing of the
      original structure

* src/matvar_struct.c (Mat_VarGetStructs): Update documentation to note
      that the structure subarray should still be free'd
Add test for indexing of structure using dimension slices

* test/struct_api.at: Added new test

* test/test_mat.c (test_struct_api_get): Added

* test/test_mat.c (main): Check for test name "struct_api_get"
Fix field of MAT variable structure holding number of bytes for large data

* src/matio.h (matvar_t): Change type of nbytes to size_t
Fix function to create variables for large data

* src/mat.c (Mat_VarCreate): Change type of nmemb, nfields, and i to size_t
Document change in behavior for memory conserve of structure fields/
cell elements

* documentation/intro.texi: Add new behavior to the list of changes, and
      add a section with a brief explanation
Add man pages for structure indexing functions

* documentation/Makefile.am: Added new man pages to dist_man3_MANS

* documentation/Mat_VarGetStructs.3,
  documentation/Mat_VarGetStructsLinear.3: Added
Change version and date for a beta release

* configure.ac: Change version to 1.5.0b1 and set date for expected release
Add function to get the library version

* src/mat.c,src/matio.h (Mat_GetLibraryVersion): Added

* documentation/Makefile.am: Added Mat_GetLibraryVersion.3 to dist_man3_MANS

* documentation/Mat_GetLibraryVersion.3: Added