Add ST_BandFileSize and ST_BandFileTimestamp, extend ST_BandMetadata()

[robe]

​https://github.com/postgis/postgis/pull/240

This is to accept Even Rouault's patch provided.

Note these functions will be used later for clients such as QGIS for aiding in viewing out-db rasters in cases where both client and server have access to the raw files to verify the files being referenced are the same.

[robe]

code committed at r16567

Load currently failing for PostgreSQL 9.5

psql:/var/lib/jenkins/workspace/postgis/branches/2.5/regress/00-regress-install/share/contrib/postgis/rtpostgis.sql:110: ERROR: could not load library "/var/lib/jenkins/workspace/postgis/branches/2.5/regress/00-regress-install/lib/rtpostgis-2.5.so": /var/lib/jenkins/workspace/postgis/branches/2.5/regress/00-regress-install/lib/rtpostgis-2.5.so: undefined symbol: UInt64GetDatum`

rtpg_band_properties.o:rtpg_band_properties.c:(.text+0x20f2): undefined reference to UInt64GetDatum' rtpg_band_properties.o:rtpg_band_properties.c:(.text+0x212d): undefined reference toUInt64GetDatum'
C:/ming64gcc48/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/4.8.3/../../../../x86_64-w64-mingw32/bin/ld.exe: rtpg_band_properties.o: bad reloc address 0x0 in section `.pdata'
collect2.exe: error: ld returned 1 exit status
E:/jenkins/postgresql/rel/pg9.5w64gcc48/lib/pgxs/src/makefiles/../../src/Makefile.shlib:388: recipe for target 'rtpostgis-2.5.dll' failed
make[2]: *** [rtpostgis-2.5.dll] Error 1
make[2]: Leaving directory '/projects/postgis/branches/2.5/raster/rt_pg'
Makefile:32: recipe for target 'pglib' failed
make[1]: *** [pglib] Error 2
make[1]: Leaving directory '/projects/postgis/branches/2.5/raster'
GNUmakefile:16: recipe for target 'all' failed
make: *** [all] Error 1